WEBVTT

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Hello, I'm Joohwan Kim

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This is the fourth class of Unreal C++ basics

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C++ Unreal Structure

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During this time, inheritance, polymorphism, and template

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are the elements of C++ that we'll learn

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And we'll learn about the C++ inheritance structure within the Unreal Engine

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And in order to implement reflection

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We'll learn about UPROPERTY and UFUNCTION

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Finally, we'll learn about the life cycle of actors

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Then after the lecture

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you will be ready for C++ programming using Unreal

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Understanding Inheritance, Polymorphism, and Template

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First, the other elements of C++

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It's actually impossible to explain all the elements of C++

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But in order to do Unreal C++ Programming

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a must-have part is

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inheritance

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We learned about class in the previous lecture

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Inheritance is collecting a certain part

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and sending it to the parent object

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So it inherits the parent

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It's like us inheriting in real life

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A certain property, or content

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Usually data and function, are inherited

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When parent class is inherited

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The daughter becomes the parent's member variable, or member function

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It becomes the member of the parent

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We can call it parent's member variable or member function, either works

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We make this inheritance because

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since we're making multiple classes

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the similar parts that overlap

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need to be reused

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That's why this grammar was made

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For example

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Birds, cats, whales

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These objects were constructed with class

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But after construction

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They had the similarity of being a living thing

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And the similarity of moving

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And the similarity of having a name

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All these parts are overlapping

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So we make a parent class called living thing

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And by inheriting that

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we make birds, cats, dogs, and whales

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The inherited form is called Class Hierarchy

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In English, it's called hierarchy

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Hierarchy is similar to a family tree

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That's also called Hierarchy

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Just like the family tree

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The parent class, the middle class

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and the bottom class are depicted

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So creating this hierarchy

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in object-oriented programming

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it corresponds to the construction part

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It's a very important part

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There's a lot of philosophy to it

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As I mentioned earlier

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Are we going to link it by similar parts

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or are we going to link them by similar forms

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or link them by similar functions

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There are various approaches

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Based on that, we would link them differently

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The things I mentioned earlier

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We may link them as living things

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or moveable

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having a name

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able to move

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able to attack, able to be hit

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Like those, they may also be classified by functions

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So in order to implement those

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What we need to know it

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Function Overriding

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We need to redefine the function

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What this means is that

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The daughter classes that inherited the parent class

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Still has the member variable of the parent

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It's not private, but more than protected

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If the access modifier is made

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The data within the parent class can be used

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As for functions

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we can also use the parent class

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But rather than the parent operation

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If we want to operate differently

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Then we do overriding

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That's why it's function overriding

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When we do function overriding

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Operating in the parent

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and operating in the daughter can be made differently

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That's called polymorphism

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It's also called dynamic binding

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Usually, we call it subtype polymorphism

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There are many types of polymorphisms

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Out of them, the sub type

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So between the parent and the daughter

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Since the sub type is made from the parent

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the polymorphism that has the form of parent-daughter relationship

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is called sub-type polymorphism

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And through polymorphisms

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By combining multiple objects into one parent

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The parent function

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Usually the virtual function, is overridden

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Using the parent function to control

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the daughter class functions

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is called abstraction

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To tell you about polymorphism further

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If we take a look at the link about polymorphism

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The page you're seeing right now

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is called GitHub

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You'll use it a lot as a programmer

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It uses the version control system called Git

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The sources that Microsoft possesses

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can be saved in this page

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If you take a look, there's a particular page

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and the 4 types of C++ polymorphism

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It says The Four Polymorphisms in C++

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It's an explanation of the four types of polymorphisms of C++

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Polymorphism exists in more than 4 types

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These days, we even say 7 types or 12 types

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To put it in simple terms

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When we do a certain operation

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It's the same operation

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But it acts differently based on the object

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It's the same command

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but it acts differently, and that's what polymorphism is

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So just like the first line, there's subtype polymorphism

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And second, parameter polymorphism

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and temporary polymorphism and forced polymorphism

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I'll only explain about the subtype polymorphism

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It's also called runtime polymorphism

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As I told you

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Linking cats, tigers, and cheetahs

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and calling them "moving", is what the example shows

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To tell you about abstraction

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Through subtype polymorphism

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a certain object is literally becoming abstracted

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Dogs, cats, and whales can all move but

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Dogs will run

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Birds will fly

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And whales will swim

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But by placing a parent object

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and calling it "move", is abstracting

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It abstracts by using polymorphism

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It's similar to hiding data using capsulation

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In summary, it's a method of abstracting class and method

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It's the method of abstraction, and it uses polymorphism

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To implement polymorphism, to implement abstraction

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The most important part of C++ grammar

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There's the virtual keyword

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When the keyword virtual is placed in front of a function

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It becomes a virtual function

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Called virtual function in English

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As I mentioned earlier

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Implementing subtype polymorphism

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It's the most normal and the only way

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In the grammar, create the virtual function in the parent

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and in the daughter, take the virtual function

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and override it

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Then when it's called from the parent

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Even though it's the same call

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It will show different operations based on the daughter type

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For overriding and virtual function, the signature has to match

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Signature, as I mentioned before

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For the signature of a function

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The return type and the parameter

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and how the function looks, are called signature

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Having the two integer parameters

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A function that has the integer return form

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Then we say that the signature is the same

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So when the signature of the parent and the daughter is the same

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The method of calling the function will also be the same

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Then through function call, we can implement polymorphism

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For polymorphism and virtual function, destructor is possible

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For destructor, when it disappears

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in order to destruct polymorphically

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it can use them

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It's impossible for constructor

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And that's because

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in the hierarchy, the parent and the daughter has to be formed

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But when the parent is constructed

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we don't know the daughter

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So it's not the target of virtual function

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Once we know virtual function, the way how virtual functions work

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or the way it compiles as one, also needs to be learned

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First, there's something called static binding

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What static binding is

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is that it's related to how the function is called over

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At the side where the function is called over to

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In order to call the function

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In order to call the function text

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they need to know the address of the function text

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So what decides the address

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When you compile, you can know the function call address

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Of course, you'll need to address when it operates

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But when it compiles

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The address that calls the function

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gets inserted into the calling part

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This is called static binding

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also called early binding

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In other words, when calling the function

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For normal functions, at the time of call

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we say that we know where the function is at

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So for normal member functions, static binding

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is done

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For normally made functions

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Whether they're member functions or not

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Since we're talking about class right now, they're member functions

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But for normal functions, they're called static

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But as before, in order to implement subtype polymorphism

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Function made as virtual function

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can be decided at the time of operation

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Because the pointer of the parent

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can point to the daughter

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But when the parent is pointing to the daughter

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The actual type may be bird, cat, or dog

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But when it receives living thing

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Until the time of calling it as living thing class

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it's usually not decided until then

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So we say that we decide the call function during runtime

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and that's called dynamic binding, or late binding

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In summary, virtual function is when

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you know the address of the function when you call

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And you know it by

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for any objects or any classes

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when you use virtual function

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Where there's at least one virtual keyword

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and it's implemented

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The 4 byte or 8 byte at the very front of the class

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The pointer forms, that points to the virtual function table

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So it includes the information of what function to call and how to call

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The pointer that points to the table, is formed

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And through the pointer

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Through the pointer of basic class

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Where the function is at

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Where the function pointer is at, is found

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This is subtype polymorphism

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It's the method of how polymorphism is formed

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We need to actually look at the code in order to understand

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That's how difficult it is at first

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So for now

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When calling with virtual function, we can know the address of the function

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Static binding, is as far as you should know

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So when making this virtual function

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Among virtual function, there's something called pure virtual function

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It's for making abstract class

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To put this in simple terms

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It's a virtual function with no content, no implementation

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The dog runs, the bird flies

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the whale swims

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We say that the living things are moving

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But the living thing may not even be there

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The target of living thing

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may not even move, is what it means

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So for abstract class that contains pure virtual function

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Instance is impossible

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It means that we can't create that class

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The concept of a living thing moving

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can't be actually made

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By creating a pointer called living thing

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we point to the dog, point to the bird

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and pointing to the whale, is possible

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It's the exact same meaning as the pointer

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So for pure virtual function

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Or abstract virtual function, doesn't create the function implementation

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It only creates the outer form of the function

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and redefine them in the daughter

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When we use this pure virtual function

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we can't actually made the object

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so we can't only make abstract classes

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We can only make abstract class

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And this means forcing abstract

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Related to virtual function, I can explain about the virtual destructor

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As I mentioned earlier, destructor is possible in virtual function

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but not constructor

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Why does destructor have virtual function?

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Within the hierarchy

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When there's the parent and daughter relationship

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00:13:07.753 --> 00:13:12.253
In order to completely destroy the daughter using the parent class

278
00:13:12.254 --> 00:13:16.054
even the destroyer is implemented virtually

279
00:13:16.654 --> 00:13:18.454
This is the virtual function table I mentioned earlier

280
00:13:18.454 --> 00:13:20.851
It's called virtual table

281
00:13:20.851 --> 00:13:24.901
There were controversies about the word virtual

282
00:13:24.902 --> 00:13:30.703
The address of the function created virtually, or dynamically

283
00:13:30.703 --> 00:13:33.903
the function pointer is included in this table

284
00:13:33.903 --> 00:13:35.901
The compiler makes this

285
00:13:35.901 --> 00:13:39.551
The implementation may be different based on how the compiler makes it

286
00:13:39.551 --> 00:13:42.750
But grammatically, when virtual function is called over

287
00:13:42.751 --> 00:13:45.151
The daughter is overridden

288
00:13:45.152 --> 00:13:48.000
in the virtual function

289
00:13:48.000 --> 00:13:49.901
If it follows the C++ standard

290
00:13:49.901 --> 00:13:52.651
So the class that uses virtual function

291
00:13:52.652 --> 00:13:54.352
has the virtual function table

292
00:13:54.353 --> 00:13:57.904
And the pointer that points to the table

293
00:13:57.904 --> 00:13:59.554
is saved in the object

294
00:14:00.150 --> 00:14:03.700
I explained about abstract and polymorphism

295
00:14:03.701 --> 00:14:07.751
For configuration of the C++ language

296
00:14:07.752 --> 00:14:10.452
For the two main elements

297
00:14:10.452 --> 00:14:13.600
Unlike C, the two main elements are

298
00:14:13.601 --> 00:14:18.901
Abstract and polymorphism are one part

299
00:14:18.902 --> 00:14:21.602
And then there's template called generic

300
00:14:21.602 --> 00:14:23.950
It's called generic programming

301
00:14:23.951 --> 00:14:26.601
It means that we can do something generally

302
00:14:26.602 --> 00:14:29.602
In C++, this grammar is called template

303
00:14:29.952 --> 00:14:34.150
This template grammar literally means template

304
00:14:34.151 --> 00:14:36.601
It sets the form

305
00:14:36.602 --> 00:14:39.902
In generic programming

306
00:14:39.903 --> 00:14:42.553
it's used as a tool

307
00:14:42.553 --> 00:14:45.650
Let's take a quick look at the MSDN page

308
00:14:45.650 --> 00:14:48.200
As I explained in other lectures

309
00:14:48.201 --> 00:14:51.501
for looking at a certain concept, the best way is

310
00:14:51.502 --> 00:14:54.152
using Microsoft's

311
00:14:54.153 --> 00:14:56.753
Visual Studio C++

312
00:14:56.753 --> 00:15:00.750
That's why is good to use Microsoft's MSDN page

313
00:15:00.750 --> 00:15:05.350
At the very top, it says 'Learn C++, C and Assembler'

314
00:15:05.351 --> 00:15:08.451
And it says template C++

315
00:15:08.601 --> 00:15:12.300
Normally, template grammar

316
00:15:12.301 --> 00:15:14.001
only exists in C++

317
00:15:14.002 --> 00:15:16.502
Template limited to C++

318
00:15:16.503 --> 00:15:19.353
Template is the basis of generic programming in C++

319
00:15:19.353 --> 00:15:21.700
There's the basic explanation

320
00:15:21.701 --> 00:15:24.001
There's the definition and usage of template

321
00:15:24.001 --> 00:15:28.050
Under here, it says C++ and there's a code

322
00:15:28.051 --> 00:15:32.251
template typename T, T minimum, const T reference

323
00:15:32.551 --> 00:15:34.600
Like this, template grammar

324
00:15:34.601 --> 00:15:36.950
is pretty complicated for a beginner

325
00:15:36.950 --> 00:15:38.550
But in the beginning

326
00:15:38.551 --> 00:15:43.151
there's the template bent bracket, called angle bracket

327
00:15:43.151 --> 00:15:46.000
Starting from the angle bracket

328
00:15:46.001 --> 00:15:48.801
typename T, then close angle bracket

329
00:15:48.801 --> 00:15:52.251
This grammar is essential for using template

330
00:15:52.251 --> 00:15:54.301
It's a must-have grammar

331
00:15:54.301 --> 00:15:57.050
And the next part that starts with T

332
00:15:57.051 --> 00:15:58.801
The typename of template

333
00:15:58.802 --> 00:16:01.152
It means that it operates on a certain T type

334
00:16:01.152 --> 00:16:03.800
So the details and the form parameter

335
00:16:03.801 --> 00:16:06.251
parameters without the form, specialization

336
00:16:06.251 --> 00:16:12.000
Template is the grammar that takes up the other 50% of C++

337
00:16:12.001 --> 00:16:14.051
So the grammar is very complicated and varies a lot

338
00:16:14.051 --> 00:16:17.000
So for modern C++

339
00:16:17.001 --> 00:16:22.101
After C++ emerging in 1979

340
00:16:22.102 --> 00:16:25.002
it continues to improve from 2011

341
00:16:25.002 --> 00:16:26.800
So it's called C++11

342
00:16:26.801 --> 00:16:28.001
After 2011

343
00:16:28.002 --> 00:16:30.402
a new version is released every 3 years

344
00:16:30.402 --> 00:16:32.400
And the new versions are mostly

345
00:16:32.401 --> 00:16:34.750
used for strengthening generic programming

346
00:16:34.750 --> 00:16:39.501
So template has various grammars and is difficult

347
00:16:39.501 --> 00:16:42.201
but if you want to use C++ well

348
00:16:42.251 --> 00:16:44.350
you must know this grammar

349
00:16:44.351 --> 00:16:46.601
So I hope you take a look at the MSDN page

350
00:16:46.601 --> 00:16:48.450
Using template

351
00:16:48.451 --> 00:16:50.201
is called compile type polymorphism

352
00:16:50.201 --> 00:16:52.101
In English, Compile Type Polymorphism

353
00:16:52.101 --> 00:16:53.500
Usually, for polymorphism

354
00:16:53.500 --> 00:16:57.700
as I explained earlier, abstract that uses virtual function

355
00:16:57.701 --> 00:17:01.101
It's usually called runtime polymorphism that uses virtual function

356
00:17:01.101 --> 00:17:03.400
The polymorphism appears at the time of operation

357
00:17:03.401 --> 00:17:06.101
But unlike that, using a template

358
00:17:06.101 --> 00:17:09.051
Compile type, or the source code

359
00:17:09.051 --> 00:17:11.201
If they're made into a binary code

360
00:17:11.202 --> 00:17:13.402
and made possible, that's called compile

361
00:17:13.402 --> 00:17:15.650
At the time of translating

362
00:17:15.651 --> 00:17:19.301
the polymorphism is operated

363
00:17:19.301 --> 00:17:22.050
So at the time of compiling

364
00:17:22.051 --> 00:17:26.451
we said that it's a tool for making a class type

365
00:17:26.451 --> 00:17:28.550
But even for the type

366
00:17:28.551 --> 00:17:31.251
Even when we don't know what type will come in

367
00:17:31.252 --> 00:17:33.202
We can still write the code

368
00:17:33.202 --> 00:17:34.351
To put it in simple terms

369
00:17:34.351 --> 00:17:38.351
I explained about the add function that adds two integers

370
00:17:38.351 --> 00:17:40.500
When we make the add function

371
00:17:40.501 --> 00:17:44.451
We don't know whether integer or float will come in

372
00:17:44.452 --> 00:17:46.252
But we can still make it

373
00:17:46.252 --> 00:17:48.700
That's the concept

374
00:17:48.701 --> 00:17:51.101
of compile type polymorphism template

375
00:17:51.101 --> 00:17:54.000
So on top of runtime polymorphism

376
00:17:54.001 --> 00:17:57.451
Runtime polymorphism is the same thing as subtype polymorphism

377
00:17:57.451 --> 00:17:59.301
The runtime polymorphism

378
00:17:59.301 --> 00:18:02.351
On top of the polymorphism that uses hierarchy

379
00:18:02.352 --> 00:18:05.002
It's also an important element of C++

380
00:18:05.803 --> 00:18:08.254
C++ Unreal Engine Structure

381
00:18:09.350 --> 00:18:12.301
So the overall form

382
00:18:12.301 --> 00:18:16.401
of C++ were touched upon

383
00:18:16.401 --> 00:18:18.200
Based on that

384
00:18:18.201 --> 00:18:22.251
let's take a look at the hierarchy structure of Unreal C++

385
00:18:22.251 --> 00:18:24.801
Visual studio 2022 community

386
00:18:24.801 --> 00:18:27.801
We're going to use this version

387
00:18:27.901 --> 00:18:30.850
And let's skim through the Unreal source code

388
00:18:30.850 --> 00:18:32.451
We didn't learn it yet

389
00:18:32.451 --> 00:18:36.751
but actor class, with A as the prefix

390
00:18:36.751 --> 00:18:40.400
actor class and character class

391
00:18:40.401 --> 00:18:42.251
For the hierarchy of the actor class series

392
00:18:42.252 --> 00:18:45.102
as we move up from the character class

393
00:18:45.103 --> 00:18:47.403
We'll take a look at the inheritance structure

394
00:18:47.404 --> 00:18:49.440
If you look at the source code

395
00:18:49.440 --> 00:18:50.945
There's a lot to explain

396
00:18:50.945 --> 00:18:55.120
But I'll just touch upon the main parts

397
00:18:55.120 --> 00:18:57.190
First, where 'sharp' is included

398
00:18:57.191 --> 00:19:00.840
Syntaxes such as sharp pragma once or sharp include

399
00:19:00.840 --> 00:19:04.280
are called pre-processors

400
00:19:04.280 --> 00:19:08.160
Before compiling, the pre-processor

401
00:19:08.160 --> 00:19:13.120
the pre-processor is commanded to change the document this way

402
00:19:13.120 --> 00:19:17.600
The pragma once is declaring that this code doesn't repeat twice

403
00:19:17.600 --> 00:19:22.439
And it says sharp include core minimal.h

404
00:19:22.439 --> 00:19:24.730
What #include is, is that

405
00:19:24.731 --> 00:19:27.381
within the source code

406
00:19:27.382 --> 00:19:29.849
other source codes are included

407
00:19:29.849 --> 00:19:34.120
So the core minimal. h header file

408
00:19:34.120 --> 00:19:36.170
is part of the source code

409
00:19:36.170 --> 00:19:39.310
That source code, in this third line

410
00:19:39.311 --> 00:19:41.711
will be copied as is

411
00:19:42.360 --> 00:19:45.709
Then there's include GameFramework/Character.h

412
00:19:45.709 --> 00:19:49.120
Same thing for this, the source code content of character.h

413
00:19:49.121 --> 00:19:51.571
will be pasted as-is here

414
00:19:51.571 --> 00:19:54.400
Then there's UCLASS and parenthesis

415
00:19:54.400 --> 00:19:59.760
This UCLASS doesn't exist in the C++ grammar

416
00:19:59.760 --> 00:20:02.120
The implementation is done by pre-processor

417
00:20:02.121 --> 00:20:05.171
but this grammar doesn't exist in C++ grammar

418
00:20:05.171 --> 00:20:07.639
But it's made with pre-processor

419
00:20:07.639 --> 00:20:11.639
It's a characteristic of C++ used in unreal

420
00:20:11.639 --> 00:20:14.880
When this UCLASS is added, it means that we'll use it in Unreal

421
00:20:14.881 --> 00:20:18.281
That's what it means

422
00:20:18.480 --> 00:20:21.440
Then there's the lowercase class

423
00:20:21.440 --> 00:20:25.400
LECTURE01_API is calling convention

424
00:20:25.400 --> 00:20:28.599
You don't need to know about this for now

425
00:20:28.599 --> 00:20:32.919
This is about how we're going to call this class

426
00:20:32.919 --> 00:20:35.080
It's a code, but we'll pass for now

427
00:20:35.080 --> 00:20:39.199
And the AMyCharacterL after that

428
00:20:39.199 --> 00:20:42.030
This is the class type of the character

429
00:20:42.031 --> 00:20:44.131
that I made in Unreal

430
00:20:44.131 --> 00:20:46.519
And next to it, there's a colon

431
00:20:46.519 --> 00:20:48.959
and says public Acharacter

432
00:20:48.959 --> 00:20:51.160
And this is the grammar of inheritance

433
00:20:51.160 --> 00:20:53.820
The name of the class

434
00:20:53.820 --> 00:20:55.670
The name of the class that I made

435
00:20:55.671 --> 00:20:57.621
is AMyCharacterL

436
00:20:57.621 --> 00:20:59.760
And this AMyCharacterL

437
00:20:59.761 --> 00:21:02.811
is the type I explained, the type of the class

438
00:21:02.960 --> 00:21:05.960
And this class, public acharacter

439
00:21:05.960 --> 00:21:08.960
has another class called acharacter as the parent

440
00:21:08.960 --> 00:21:11.639
That's what this inheritance grammar means

441
00:21:11.639 --> 00:21:14.199
As I mentioned earlier, it corresponds to the inheritance

442
00:21:14.199 --> 00:21:16.119
It has the parent called acharacter

443
00:21:16.119 --> 00:21:18.370
With the acharacter parent

444
00:21:18.371 --> 00:21:20.521
we made the AMyCharacterL

445
00:21:20.521 --> 00:21:23.919
For the generate body inside the braces

446
00:21:23.919 --> 00:21:26.000
it's the code made in Unreal

447
00:21:26.000 --> 00:21:29.880
I'll also explain about this later when I talk about reflection

448
00:21:29.880 --> 00:21:33.919
There are codes that Unreal creates and inserts

449
00:21:33.919 --> 00:21:35.850
For the existing C++

450
00:21:35.851 --> 00:21:38.701
reflection function is not possible

451
00:21:38.701 --> 00:21:42.020
It's not provided in the language

452
00:21:42.020 --> 00:21:45.080
But to implement that, Unreal has made it

453
00:21:45.080 --> 00:21:47.160
I'll explain about it later

454
00:21:47.160 --> 00:21:50.600
And there's public modifier

455
00:21:50.600 --> 00:21:51.399
There's the comment

456
00:21:51.399 --> 00:21:55.320
and the constructor called AMyCharacterL

457
00:21:55.320 --> 00:21:58.720
And after that, public void BeginPlay

458
00:21:58.720 --> 00:22:00.420
When this actor begins

459
00:22:00.421 --> 00:22:02.371
this is what's called

460
00:22:02.800 --> 00:22:04.880
tick is called at every frame

461
00:22:04.880 --> 00:22:06.160
It says it in English at the top

462
00:22:06.160 --> 00:22:07.479
Called every frame

463
00:22:07.479 --> 00:22:10.919
or called when the game starts or when spawned

464
00:22:10.919 --> 00:22:14.160
The time that these functions will be called

465
00:22:14.160 --> 00:22:16.240
are described in Unreal

466
00:22:16.240 --> 00:22:18.919
For begin play, tick, setup player, and input component

467
00:22:18.919 --> 00:22:22.080
they're all declared as virtual

468
00:22:22.080 --> 00:22:24.320
virtual void, and void is the return type

469
00:22:24.320 --> 00:22:26.040
Virtual, as I mentioned earlier

470
00:22:26.041 --> 00:22:28.841
is the keyword that shows that it's a virtual function

471
00:22:29.240 --> 00:22:32.759
At the back, there's the keyword override

472
00:22:32.759 --> 00:22:34.439
Looking at this

473
00:22:34.440 --> 00:22:37.040
this function was implemented in the parent

474
00:22:37.040 --> 00:22:41.600
and was redefined in the daughter

475
00:22:41.600 --> 00:22:43.560
So the very bottom part

476
00:22:43.561 --> 00:22:46.211
the most daughter of the hierarchy

477
00:22:46.360 --> 00:22:50.880
was this AMyCharacterL class that I created

478
00:22:50.880 --> 00:22:54.880
This AMyCharacterL class inherited from

479
00:22:54.880 --> 00:22:57.960
character a, the parent right above it

480
00:22:57.960 --> 00:23:00.399
Right-click on it in visual studio

481
00:23:00.400 --> 00:23:02.100
and go to definition

482
00:23:02.199 --> 00:23:04.679
Then we can go to the definition of the object

483
00:23:04.679 --> 00:23:07.600
It's the function of the visual studio itself

484
00:23:07.600 --> 00:23:11.040
That's how I moved to the parent right above it

485
00:23:11.040 --> 00:23:13.959
To go back, the class I made earlier

486
00:23:13.959 --> 00:23:15.839
is the character that I made

487
00:23:15.839 --> 00:23:17.799
And in the character I made

488
00:23:17.799 --> 00:23:21.079
there will be functions exclusive to my character

489
00:23:21.079 --> 00:23:22.399
And the a character above it

490
00:23:22.399 --> 00:23:26.040
is a class made by Unreal Engine

491
00:23:26.040 --> 00:23:27.740
Here, normally

492
00:23:27.741 --> 00:23:30.041
it contains how the character is supposed to act

493
00:23:30.041 --> 00:23:33.559
We can't take a look at the entire source, but

494
00:23:33.559 --> 00:23:37.740
the thousands of functions

495
00:23:37.740 --> 00:23:40.519
of Unreal, called api

496
00:23:40.519 --> 00:23:43.799
We can't take a look at the whole Application Programming Interface

497
00:23:43.799 --> 00:23:47.600
but generally, when I make a certain class

498
00:23:47.600 --> 00:23:49.819
at the top

499
00:23:49.820 --> 00:23:52.520
to see what code that Unreal makes

500
00:23:52.520 --> 00:23:56.219
I'm looking through the sources

501
00:23:56.219 --> 00:24:00.659
It says class ACharacter : public APawn

502
00:24:00.659 --> 00:24:04.249
It means that it made the class, or character, by inheriting Pawn

503
00:24:04.659 --> 00:24:07.219
Same thing here, in GenerateBody

504
00:24:07.219 --> 00:24:10.929
codes for reflection made by Unreal were inserted

505
00:24:11.379 --> 00:24:14.628
Underneath, it says DefaultUObjectConstruct

506
00:24:14.628 --> 00:24:16.669
In order to Unreal to use them

507
00:24:16.819 --> 00:24:20.019
the basic codes are listed here

508
00:24:20.379 --> 00:24:22.499
Similarly, if we move up one step again

509
00:24:22.500 --> 00:24:24.800
There class APawn

510
00:24:24.800 --> 00:24:27.659
Pawn is just like the Pawn of chess

511
00:24:27.659 --> 00:24:29.129
It's lower than the actor

512
00:24:29.130 --> 00:24:30.430
but higher than the character

513
00:24:30.430 --> 00:24:32.239
It's moveable

514
00:24:32.239 --> 00:24:34.258
It doesn't have characteristics

515
00:24:34.338 --> 00:24:36.909
but an object that can be moved

516
00:24:36.978 --> 00:24:39.859
It will be helpful to read the top explanation

517
00:24:39.859 --> 00:24:43.209
Pawn is the base class of all actors

518
00:24:43.210 --> 00:24:46.460
that can be possessed by players or AI

519
00:24:46.460 --> 00:24:48.648
Players or AI

520
00:24:48.648 --> 00:24:51.379
The players or AI can

521
00:24:51.379 --> 00:24:53.909
possess, but it basically means moveable

522
00:24:54.018 --> 00:24:56.459
The objects that can be possessed and moveable

523
00:24:56.459 --> 00:24:58.619
are made here, is what it's trying to say

524
00:24:58.699 --> 00:25:01.119
So when you take a look at APawn class

525
00:25:01.119 --> 00:25:03.828
there are actions that only Pawns can do

526
00:25:04.339 --> 00:25:06.778
Under that, the purple part

527
00:25:06.778 --> 00:25:08.589
the parts written in purple

528
00:25:08.590 --> 00:25:11.619
are what pre-processors redefined

529
00:25:11.619 --> 00:25:14.099
The purple parts

530
00:25:14.738 --> 00:25:17.699
in C++ or C language itself

531
00:25:17.699 --> 00:25:20.058
is not included

532
00:25:20.058 --> 00:25:21.749
The pre-processor was used

533
00:25:22.019 --> 00:25:24.939
to create the reflection function

534
00:25:24.939 --> 00:25:27.718
that doesn't exist

535
00:25:28.299 --> 00:25:29.858
Later on, when I explain reflection

536
00:25:29.858 --> 00:25:31.649
GenerateBody, UProperty

537
00:25:31.650 --> 00:25:33.650
and UFunction will all be explained

538
00:25:34.619 --> 00:25:38.219
Anyways, that's how APawn hierarchy is made up

539
00:25:38.219 --> 00:25:44.299
For Pawn, GetLifetimeReplicateProperty or PreReplication can be used

540
00:25:44.299 --> 00:25:47.858
Replication literally means that the object can be replicated

541
00:25:47.858 --> 00:25:49.579
It means moving the same way

542
00:25:49.579 --> 00:25:50.979
That's not what I'll explain right now

543
00:25:51.019 --> 00:25:53.358
This Pawn does a certain job

544
00:25:53.619 --> 00:25:56.998
It has the function of being possessed and moved

545
00:25:57.019 --> 00:25:58.598
is what we can know from this

546
00:25:58.738 --> 00:26:01.409
When I moved back to the character, the character

547
00:26:01.738 --> 00:26:03.918
wasn't that different from Pawn

548
00:26:03.919 --> 00:26:06.529
When we move up to Pawn and move up one more step

549
00:26:06.539 --> 00:26:08.299
We come across the Actor

550
00:26:08.299 --> 00:26:10.659
Before I explain the Actor

551
00:26:10.659 --> 00:26:14.109
When you take a look at Class APawn

552
00:26:14.179 --> 00:26:16.739
There's colon and Public AActor

553
00:26:16.739 --> 00:26:19.898
then comma, then Public INavAgentInterface

554
00:26:19.898 --> 00:26:22.058
This is called multiple inheritance

555
00:26:22.058 --> 00:26:24.698
There's more than one parent

556
00:26:24.698 --> 00:26:26.498
It can inherit from multiple

557
00:26:26.659 --> 00:26:30.418
But I won't mention this multiple inheritance for now

558
00:26:30.418 --> 00:26:33.259
So it inherited two things

559
00:26:33.858 --> 00:26:36.058
Interface Navigation Agent Interface

560
00:26:36.058 --> 00:26:37.978
I stands for Interface

561
00:26:37.978 --> 00:26:40.898
Rather than going to INavigationAgentInterface

562
00:26:40.898 --> 00:26:42.898
we'll move up to Actor class

563
00:26:42.898 --> 00:26:45.659
If we go to AActor class again

564
00:26:45.659 --> 00:26:47.819
This becomes the parent of Pawn

565
00:26:47.819 --> 00:26:49.659
It's the parent of Pawn

566
00:26:49.659 --> 00:26:52.379
Same thing, there's the actor for the parent of Pawn

567
00:26:52.379 --> 00:26:55.138
And how this Actor acts

568
00:26:55.138 --> 00:26:57.498
The top part is similar

569
00:26:57.498 --> 00:27:00.258
But there's something called InitializeDefaults

570
00:27:00.258 --> 00:27:01.698
If you look at the explanation

571
00:27:01.698 --> 00:27:04.258
Called from the constructor to initialize the class

572
00:27:04.258 --> 00:27:05.739
to its default setting

573
00:27:05.739 --> 00:27:07.379
Using the default setting

574
00:27:07.379 --> 00:27:10.498
this object

575
00:27:10.498 --> 00:27:13.248
will be initialized

576
00:27:13.248 --> 00:27:16.208
So as you've seen so far

577
00:27:16.258 --> 00:27:18.979
We can move up even more, but up until this hierarchy

578
00:27:19.138 --> 00:27:22.719
Starting from AMyCharacterL

579
00:27:22.719 --> 00:27:25.579
to ACharacter

580
00:27:25.579 --> 00:27:27.258
APawn

581
00:27:27.258 --> 00:27:28.549
AActor

582
00:27:28.579 --> 00:27:31.459
Until then, there are many parent hierarchy

583
00:27:31.459 --> 00:27:33.299
This is called inheritance hierarchy

584
00:27:33.299 --> 00:27:35.978
We divide it into so many hierarchy because

585
00:27:35.978 --> 00:27:38.618
for each hierarchy, for each parent

586
00:27:38.618 --> 00:27:41.299
there are various and complex works that need to be done

587
00:27:41.299 --> 00:27:42.988
That's why it's configured like this

588
00:27:43.099 --> 00:27:45.219
The explanation was long

589
00:27:45.219 --> 00:27:48.118
But we have one or two more steps left

590
00:27:48.138 --> 00:27:52.198
Let's go to UObject, the parent of Actor

591
00:27:52.498 --> 00:27:55.898
UObject is actually the parent

592
00:27:55.898 --> 00:27:58.998
of almost all objects that exist in Unreal

593
00:27:59.179 --> 00:28:02.228
There's one more step, but first for UObject

594
00:28:02.338 --> 00:28:04.418
For UObject

595
00:28:04.539 --> 00:28:06.579
it's also explained on top in English

596
00:28:06.579 --> 00:28:10.659
The Base Class of all UE objects

597
00:28:10.659 --> 00:28:14.018
For all the objects that appear in Unreal Engine

598
00:28:14.018 --> 00:28:14.939
this is the base class

599
00:28:14.939 --> 00:28:17.379
Hence the name, it's the basic class

600
00:28:17.379 --> 00:28:18.859
Of course, there's another parent at the top

601
00:28:18.859 --> 00:28:21.898
But this is the hierarchy for implementing functional aspects

602
00:28:22.219 --> 00:28:25.539
This class, UObject, is actually

603
00:28:25.539 --> 00:28:28.419
very important for Unreal C++ Programming

604
00:28:28.419 --> 00:28:30.379
It's the most basic

605
00:28:30.379 --> 00:28:33.178
It can act most normally

606
00:28:33.178 --> 00:28:35.219
It's the class that you must know

607
00:28:35.219 --> 00:28:37.099
There are lots of grammars

608
00:28:37.099 --> 00:28:39.699
and I can't explain every one of them

609
00:28:39.699 --> 00:28:41.778
as Unreal is the world's most

610
00:28:41.778 --> 00:28:43.618
AAA class engine

611
00:28:43.618 --> 00:28:45.659
The content is very complicated

612
00:28:45.659 --> 00:28:48.778
and the explanation and the implementation are also complicated

613
00:28:48.778 --> 00:28:51.539
But through the Pawn and Actor

614
00:28:51.539 --> 00:28:53.898
moving up the hierarchy

615
00:28:53.898 --> 00:28:56.778
moving up to the UObject

616
00:28:56.778 --> 00:28:59.309
is what's important

617
00:28:59.578 --> 00:29:01.069
Same thing, at the top

618
00:29:01.069 --> 00:29:03.939
There's a slash, not two slashes, but slash asterisk

619
00:29:04.058 --> 00:29:06.578
Starting from slash asterisk

620
00:29:06.859 --> 00:29:09.759
the first four lines are the comment

621
00:29:09.939 --> 00:29:11.458
The comment doesn't get compiled

622
00:29:11.458 --> 00:29:13.998
It's an explanation, so take a look

623
00:29:13.998 --> 00:29:18.298
Same thing for document.unrealengine.com

624
00:29:18.298 --> 00:29:19.699
The explanation in Unreal engine

625
00:29:19.699 --> 00:29:22.298
take a look at that as well

626
00:29:22.298 --> 00:29:24.298
Then the things I've said so far

627
00:29:24.298 --> 00:29:26.778
will be understood in detail

628
00:29:26.778 --> 00:29:29.298
So if you take a look at UObject for a second

629
00:29:29.298 --> 00:29:32.458
There's Virtual Constructor

630
00:29:32.458 --> 00:29:36.458
probably virtual function constructor

631
00:29:36.458 --> 00:29:39.219
will also be callable

632
00:29:39.219 --> 00:29:40.659
Config Name, Static Config Name

633
00:29:40.659 --> 00:29:44.618
We'll be able to name static names as well

634
00:29:44.618 --> 00:29:46.139
The normal things that we can do

635
00:29:46.139 --> 00:29:49.298
The thing that all Unreal objects can do

636
00:29:49.298 --> 00:29:52.519
are what's written here

637
00:29:52.819 --> 00:29:55.338
While we're on it

638
00:29:55.338 --> 00:29:59.018
I said that Unreal Object is the parent

639
00:29:59.018 --> 00:30:01.018
of practically all the objects that appear in Unreal

640
00:30:01.018 --> 00:30:02.618
But let's go to the very top

641
00:30:02.618 --> 00:30:05.778
So Unreal Object is Unreal Object Base Utility

642
00:30:05.778 --> 00:30:07.618
The basic actions

643
00:30:07.618 --> 00:30:11.298
The basic useful utilities are included

644
00:30:11.298 --> 00:30:14.469
And when you take a look, there seems to be functions

645
00:30:14.738 --> 00:30:17.609
As for MarkPendingKill

646
00:30:17.898 --> 00:30:21.099
There's something called Garbage Collecting

647
00:30:21.099 --> 00:30:23.738
where objects need to be removed someday

648
00:30:23.738 --> 00:30:26.178
This is the hierarchy that holds those functions

649
00:30:26.178 --> 00:30:29.819
You can see Clear Garbage or Mark As Garbage Clear Pending

650
00:30:29.819 --> 00:30:33.859
But for this UObjectBaseUtility hierarchy

651
00:30:33.859 --> 00:30:35.939
The object is created and deleted

652
00:30:35.939 --> 00:30:39.379
in this class

653
00:30:39.379 --> 00:30:41.498
Let's move up to UObjectBase

654
00:30:41.498 --> 00:30:44.458
This is the uppermost, without a parent

655
00:30:44.458 --> 00:30:45.898
hierarchy that we're at

656
00:30:45.900 --> 00:30:52.300
UObject was called BaseOfU earlier because

657
00:30:52.300 --> 00:30:55.200
when it operates

658
00:30:55.201 --> 00:30:57.801
conceptually, the parent is UObject

659
00:30:58.100 --> 00:31:01.300
But UObject can't be made at once as well

660
00:31:01.300 --> 00:31:04.000
So for UObject, in Unreal

661
00:31:04.001 --> 00:31:07.301
It needs a lot of functions as the parent of all objects

662
00:31:07.301 --> 00:31:11.100
That's why there are two more hierarchy above it

663
00:31:11.100 --> 00:31:14.600
Then at the very top

664
00:31:14.600 --> 00:31:17.200
That's why the name is UObjectBase

665
00:31:17.200 --> 00:31:19.750
When making Unreal object

666
00:31:19.751 --> 00:31:24.251
this is the basic class

667
00:31:24.500 --> 00:31:27.599
In the comment, it says Low Level Implementation of UObject

668
00:31:27.599 --> 00:31:31.099
Literally translates to its meaning

669
00:31:31.099 --> 00:31:34.500
So it means making the most basic, at the low level

670
00:31:34.500 --> 00:31:36.599
Should not be used directly in game code

671
00:31:36.599 --> 00:31:39.299
So we can't use this right away in game code

672
00:31:39.299 --> 00:31:42.500
There's a keyword called Friend, and to explain this briefly

673
00:31:42.500 --> 00:31:47.100
This means that rather than going to other class or qualifier

674
00:31:47.101 --> 00:31:48.900
we can use it right away

675
00:31:48.900 --> 00:31:53.200
Normally, to keep all Private Projected and Public

676
00:31:53.400 --> 00:31:56.900
they have to pass through all capsulation

677
00:31:56.900 --> 00:31:59.800
But without those, they can access each other

678
00:31:59.900 --> 00:32:04.150
So they set that as Friend class or Friend Struct

679
00:32:04.199 --> 00:32:08.649
Here as well, there's the basic form of constructor

680
00:32:08.649 --> 00:32:12.599
And the name, the package name

681
00:32:12.599 --> 00:32:15.000
It says super class, static class

682
00:32:15.000 --> 00:32:18.300
So the name and where it belongs to

683
00:32:18.400 --> 00:32:21.500
Only those basic things

684
00:32:21.501 --> 00:32:23.051
are included here

685
00:32:23.400 --> 00:32:25.801
So to recall

686
00:32:25.801 --> 00:32:28.099
Using the source code

687
00:32:28.099 --> 00:32:29.600
in the example of lecture 1

688
00:32:29.601 --> 00:32:32.501
The character class, MyCharacter class that we made

689
00:32:32.800 --> 00:32:37.700
We went through each hierarchy using the source code

690
00:32:37.700 --> 00:32:40.500
Starting from Begin, Play, Tick, the overridden parts

691
00:32:40.699 --> 00:32:44.800
then up to the middle hierarchy, Garbage Collecting, and handling objects

692
00:32:44.800 --> 00:32:47.500
Then up to the Actor

693
00:32:47.500 --> 00:32:50.400
And the Unreal Object, the parent of all, and UObject, the base of all

694
00:32:50.400 --> 00:32:53.050
In order to implement the UObject

695
00:32:53.051 --> 00:32:55.301
we also took a look at the two class hierarchies

696
00:32:55.600 --> 00:32:59.800
Even the programmers who can handle C++ well

697
00:32:59.800 --> 00:33:04.899
have a hard time looking at the Unreal class hierarchy

698
00:33:04.899 --> 00:33:09.249
So when you have just learned C++

699
00:33:09.250 --> 00:33:11.700
it may be difficult to read these codes

700
00:33:11.700 --> 00:33:14.000
But when you do Unreal programming

701
00:33:14.000 --> 00:33:19.000
you'll see them often, so I skimmed through them

702
00:33:19.000 --> 00:33:21.800
The UProperty and UFunction I mentioned earlier

703
00:33:21.800 --> 00:33:25.650
I'll explain about the reflection system of Unreal

704
00:33:25.699 --> 00:33:30.699
Actually, this isn't the details of C++

705
00:33:30.800 --> 00:33:32.950
It's not the C++ Specification

706
00:33:32.951 --> 00:33:34.801
And it's not implemented in C++

707
00:33:34.801 --> 00:33:38.700
It's not implemented in C++ language

708
00:33:38.701 --> 00:33:41.251
so Unreal made this system

709
00:33:41.399 --> 00:33:43.900
To explain this briefly

710
00:33:43.900 --> 00:33:47.500
When there's a syntax that says int a = 3

711
00:33:47.699 --> 00:33:50.049
In variable a

712
00:33:50.050 --> 00:33:52.750
3 can be included or used

713
00:33:52.750 --> 00:33:56.000
But we don't know that the name of the variable is a

714
00:33:56.000 --> 00:33:58.850
When the program is executed

715
00:33:58.850 --> 00:34:02.100
we can't know the name of the variable and the class

716
00:34:02.199 --> 00:34:07.249
Even in the current C++2023

717
00:34:07.249 --> 00:34:09.899
That's the newest version

718
00:34:09.899 --> 00:34:12.550
Even in the C++ released in 2023

719
00:34:12.550 --> 00:34:14.749
The name of the variable or the name of the class

720
00:34:14.750 --> 00:34:16.650
cannot be brought as text

721
00:34:16.650 --> 00:34:20.899
So using the existing grammar, we need to implement it somehow

722
00:34:20.899 --> 00:34:22.699
To see what class I made

723
00:34:22.699 --> 00:34:25.899
And what variables and functions are there

724
00:34:25.899 --> 00:34:27.300
From outside the program

725
00:34:27.301 --> 00:34:29.851
Being able to see those outside the source code

726
00:34:29.851 --> 00:34:31.800
is called the Reflection system

727
00:34:31.800 --> 00:34:35.050
In order to implement the Unreal's Reflection system

728
00:34:35.050 --> 00:34:37.199
If you look at Unreal engine

729
00:34:37.199 --> 00:34:38.500
When you click on Actor

730
00:34:38.501 --> 00:34:42.301
You can see the inner properties of Actor

731
00:34:42.301 --> 00:34:44.100
Those are possible because

732
00:34:44.100 --> 00:34:47.650
And we can call a function of an Actor

733
00:34:47.650 --> 00:34:49.499
We can call it from the server

734
00:34:49.500 --> 00:34:53.550
And other clients can call as well because

735
00:34:53.550 --> 00:34:57.700
This Reflection function that works with UProperty and UFunction

736
00:34:57.700 --> 00:34:59.800
is coming into play

737
00:34:59.800 --> 00:35:02.099
I skipped in the middle

738
00:35:02.099 --> 00:35:03.800
but to summarize it

739
00:35:03.800 --> 00:35:07.099
Many implementations are skipped, actually

740
00:35:07.099 --> 00:35:09.700
UProperty is placed in front of the member variable

741
00:35:09.799 --> 00:35:13.800
If we put UProperty Define before the variable

742
00:35:13.800 --> 00:35:15.299
The pre-processor

743
00:35:15.299 --> 00:35:19.399
Then that means that this variable will be used in the Reflection system

744
00:35:19.399 --> 00:35:22.200
Same thing for UFunction, it's used in member function

745
00:35:22.200 --> 00:35:25.500
Existing in C++ as well

746
00:35:25.500 --> 00:35:27.600
UClass, UEnumerate

747
00:35:27.600 --> 00:35:30.899
I didn't explain Enumerate, but

748
00:35:30.899 --> 00:35:34.100
it's a countable form

749
00:35:34.100 --> 00:35:35.899
It's put as a special reason

750
00:35:35.899 --> 00:35:38.899
There's a keyword called UStruct

751
00:35:38.899 --> 00:35:41.799
As I explained, since it doesn't have the Reflection function

752
00:35:41.799 --> 00:35:46.100
When we make one C++ file in Unreal

753
00:35:46.100 --> 00:35:48.000
when we make the class

754
00:35:48.000 --> 00:35:52.000
For example, after ACharacterL

755
00:35:52.000 --> 00:35:55.899
Generated.h file is formed automatically

756
00:35:55.899 --> 00:36:00.500
And this becomes included in Generated Body

757
00:36:00.700 --> 00:36:03.700
Unreal's Reflection system is

758
00:36:03.700 --> 00:36:10.100
not something we can talk about within 5 or 10 minutes

759
00:36:10.100 --> 00:36:12.500
It's made very complex

760
00:36:12.500 --> 00:36:13.799
But when we actually use it

761
00:36:13.799 --> 00:36:17.300
You just need to see that UProperty and UFunction are together

762
00:36:17.300 --> 00:36:19.300
So within the source code that I showed you earlier

763
00:36:19.300 --> 00:36:22.000
Go to AMyCharacterL

764
00:36:22.000 --> 00:36:23.849
and look at the GenerateBody

765
00:36:23.849 --> 00:36:26.399
or the UProperty above it

766
00:36:26.700 --> 00:36:30.650
Finally, I'll show you the life cycle of an Actor

767
00:36:30.700 --> 00:36:33.050
The purpose of my lecture is

768
00:36:33.299 --> 00:36:37.150
being able to do Unreal Programming using C++

769
00:36:37.151 --> 00:36:40.201
That's the step I wanted to reach

770
00:36:40.399 --> 00:36:42.450
So opening Unreal

771
00:36:42.500 --> 00:36:46.150
and changing and moving the actor

772
00:36:46.151 --> 00:36:47.651
won't be done

773
00:36:47.700 --> 00:36:50.599
But for Actor, Pawn, or Character

774
00:36:50.700 --> 00:36:52.000
when you do Unreal programming

775
00:36:52.001 --> 00:36:54.551
They're the very first object that you encounter

776
00:36:54.600 --> 00:36:57.750
So we'll take a look at the Actor's life cycle

777
00:36:57.750 --> 00:37:02.000
Click the Unreal Documentation Actors Life Cycle link

778
00:37:02.000 --> 00:37:04.000
And this screen appears

779
00:37:04.000 --> 00:37:06.750
There's a simple Breakdown

780
00:37:06.750 --> 00:37:11.399
This shows what happens when the Unreal Actor is formed

781
00:37:11.399 --> 00:37:14.100
You'll see this later

782
00:37:14.100 --> 00:37:18.700
For Actor, there are 3 main ways

783
00:37:18.700 --> 00:37:21.051
of how the life cycle works

784
00:37:21.051 --> 00:37:23.050
When it's executed in Editor

785
00:37:23.051 --> 00:37:25.701
or when it's loaded from data

786
00:37:25.701 --> 00:37:28.600
and third is when it's created dynamically

787
00:37:28.600 --> 00:37:30.999
The yellow on the left

788
00:37:31.000 --> 00:37:33.400
says Play in Editor

789
00:37:33.400 --> 00:37:36.950
What happens when the player button is pressed in Editor

790
00:37:36.950 --> 00:37:41.150
It means copying it from Editor and running it in engine

791
00:37:41.150 --> 00:37:44.450
For the second, there's a level, and the map is loaded on the level

792
00:37:44.450 --> 00:37:46.350
or when it's added in the world

793
00:37:46.399 --> 00:37:49.999
The actor is formed by bringing it from the disk

794
00:37:50.000 --> 00:37:52.300
On the right, it starts from nothing

795
00:37:52.301 --> 00:37:54.351
When an action actually happens

796
00:37:54.351 --> 00:37:56.950
For example pressing a key or colliding

797
00:37:56.950 --> 00:38:00.000
The Spawn, or Actor is dynamically created

798
00:38:00.000 --> 00:38:01.799
The Spawn Actor is created right away

799
00:38:01.799 --> 00:38:06.750
And Spawn Actor Deferred is the delayed spawn

800
00:38:06.750 --> 00:38:10.500
So it's created dynamically and about what happens next

801
00:38:10.500 --> 00:38:13.650
It's a step process

802
00:38:13.650 --> 00:38:16.350
If you look at the bottom

803
00:38:16.351 --> 00:38:17.801
It's created

804
00:38:17.801 --> 00:38:22.750
It begins play through Begin Play

805
00:38:22.750 --> 00:38:26.300
In the middle, where it says The application is running and the actor is ticking

806
00:38:26.300 --> 00:38:28.300
This is where the game is actually running

807
00:38:28.300 --> 00:38:30.200
The green part in the middle

808
00:38:30.200 --> 00:38:35.600
The game ultimately goes around a tick

809
00:38:35.600 --> 00:38:37.299
It's an infinite loop

810
00:38:37.299 --> 00:38:40.499
So it goes around the loop infinitely and runs the game

811
00:38:40.500 --> 00:38:43.799
Based on the 6 conditions on the bottom

812
00:38:43.799 --> 00:38:47.299
When it ends, go to End Play

813
00:38:47.500 --> 00:38:49.900
and it reaches the step of deleting the object

814
00:38:49.900 --> 00:38:51.600
So for Actor mark, as I explained earlier

815
00:38:51.600 --> 00:38:54.849
does Garbage Collecting and Pending Kill

816
00:38:54.849 --> 00:38:56.450
and once everything is over

817
00:38:56.451 --> 00:38:58.251
After the post processing

818
00:38:58.251 --> 00:39:01.849
BeginDestroy, IsReadyforFinishDestroy, then FinishDestroy

819
00:39:01.849 --> 00:39:05.000
It ends by destroying the object

820
00:39:05.000 --> 00:39:09.799
You're going to go through these kinds of programming

821
00:39:09.799 --> 00:39:15.500
And I hope the C++ programming basics today was helpful

822
00:39:15.500 --> 00:39:18.799
And same thing for MSDN, Microsoft Development Network, but

823
00:39:18.799 --> 00:39:21.299
when you study Unreal

824
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The Epic Games that made Unreal

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Their Documentation page will be the most helpful

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I'll end the lecture here, thank you

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Understanding inheritance, polymorphism, and template
Inheritance
Inherit the parent object for the common parts, can use the data and functions of the parent

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Need inheritance to reuse the repeated parts
Redefining function is needed to implement the inheritance hierarchy

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Polymorphism
Executing different actions with the same commands, based on different object
Subtype polymorphism: applied on daughter type that comes from the parent type

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Compile-Time Polymorphism: uses template

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Template
Name of the C++ normalization programming
Essential grammar template for using template 〈typename T〉

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C++ Unreal Engine Structure
Unreal C++ Inheritance Hierarchy

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AMyCharacterL 〈 ACharacter 〈 APawn 〈 AActor 〈 UObject 〈 UObjectBaseUtility 〈 UObjectBase

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Unreal's Reflection System
Made by Unreal because there's no reflection function in C++
Can view the variables and functions within the class from outside the source code

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Can call over the properties or functions of an Actor
UPROPERTY in front of member variable
UFUNCTION in front of member function

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The End