UE_反射系统（虚幻编译系统）
UCLASS、UFUNCTION、UPROPERTY
UCLASS 宏的有效关键字
https://docs.unrealengine.com/4.27/en-US/ProgrammingAndScripting/GameplayArchitecture/Classes/Specifiers/
When declaring classes, Class Specifiers can be added to the declaration to control how the class behaves with various aspects of the Engine and Editor.
When declaring classes, interfaces, structs, enums, enum values, functions, or properties, you can add Metadata Specifiers to control how they interact with various aspects of the engine and editor. Each type of data structure or member has its own list of Metadata Specifiers.
