UObject

//UObjectBase.h
...
private:
	/** Flags used to track and report various object states. This needs to be 8 byte aligned on 32-bit
	    platforms to reduce memory waste */
	EObjectFlags					ObjectFlags;

	/** Index into GObjectArray...very private. */
	int32							InternalIndex;

	/** Class the object belongs to. */
	UClass*							ClassPrivate;

	/** Name of this object */
	FName							NamePrivate;

	/** Object this object resides in. */
	UObject*						OuterPrivate;
    
  ...
  
public:
	FORCEINLINE uint32 GetUniqueID() const
	{
		return (uint32)InternalIndex;
	}

	/** Returns the UClass that defines the fields of this object */
	FORCEINLINE UClass* GetClass() const
	{
		return ClassPrivate;
	}
	
	/** Returns the UObject this object resides in */
	FORCEINLINE UObject* GetOuter() const
	{
		return OuterPrivate;
	}

	/** Returns the logical name of this object */
	FORCEINLINE FName GetFName() const
	{
		return NamePrivate;
	}
...

EObjectFlags ObjectFlags

비트플래그의 일종으로 UObject의 다양한 상태를 나타내기 위해서 사용한다.

Unreal docs EObjectFlags

int32 InternalIndex

UObject가 생성되면 GUObjectArray에 등록되며 그 곳의 인덱스 역할을 한다.

//UObjectHash.cpp
...
FUObjectArray GUObjectArray; //Global로 선언되어 있다.
...

//UObjectArray.h
class COREUOBJECT_API FUObjectArray
{
public:
	...
	//ObjAvailableList에서 할당 가능한 Index를 찾아서 할당
	void AllocateUObjectIndex(class UObjectBase* Object, bool bMergingThreads = false);
     
     //ObjAvailableList에 Index를 반환하여 할당 가능한 Index로 만들어 준다.
	void FreeUObjectIndex(class UObjectBase* Object);
	...
private:
	...
	/** First index into objects array taken into account for GC.							*/
	int32 ObjFirstGCIndex;
	/** Index pointing to last object created in range disregarded for GC.					*/
	int32 ObjLastNonGCIndex;
	...
    /** Array of all live objects.											*/
	TUObjectArray ObjObjects;
    /** Available object indices.											*/
	TLockFreePointerListUnordered<int32, PLATFORM_CACHE_LINE_SIZE> ObjAvailableList;
}

UClass* ClassPrivate

UObject가 어느 클래스에 속하는지 알려주는 포인터

FName NamePrivate

인스턴스의 이름이며 다음과 같은 함수의 호출로 Unique한 이름이 만들어진다.

//UObjectGlobals.cpp
FName MakeUniqueObjectName
(UObject* Parent, const UClass* Class, FName InBaseName/*=NAME_None*/);

새로운 Object의 생성에서 관여하는 StaticAlloacateObject함수 내에서 사용된다.

UObject* StaticAllocateObject
(
	const UClass*	InClass,
	UObject*		InOuter,
	FName			InName,
	EObjectFlags	InFlags,
	EInternalObjectFlags InternalSetFlags,
	bool bCanRecycleSubobjects,
	bool* bOutRecycledSubobject,
	UPackage* ExternalPackage
)
{
...
	if(InName == NAME_None)
	{
#if WITH_EDITOR
		if ( GOutputCookingWarnings && GetTransientPackage() != InOuter->GetOutermost() )
		{
			static const FName NAME_UniqueObjectNameForCooking(TEXT("UniqueObjectNameForCooking"));
			InName = MakeUniqueObjectName(InOuter, InClass, NAME_UniqueObjectNameForCooking);
		}
		else
#endif
		{
			InName = MakeUniqueObjectName(InOuter, InClass);
		}
	}
...
}

UObject OuterPrivate

object resides in OuterPrivate

//obj.cpp
UObject* UObject::CreateDefaultSubobject(FName SubobjectFName, UClass* ReturnType, UClass* ClassToCreateByDefault, bool bIsRequired, bool bIsTransient)
{
	FObjectInitializer* CurrentInitializer = FUObjectThreadContext::Get().TopInitializer();
	...
	return CurrentInitializer->CreateDefaultSubobject(this, SubobjectFName, ReturnType, ClassToCreateByDefault, bIsRequired, bIsTransient);
}

//UObejctGlobals.cpp
UObject* FObjectInitializer::CreateDefaultSubobject(UObject* Outer, FName SubobjectFName, UClass* ReturnType, UClass* ClassToCreateByDefault, bool bIsRequired, bool bIsTransient) const
{
	...
	UObject* Result = NULL;
	...
			Params.Outer = Outer;
			Params.Name = SubobjectFName;
			Params.SetFlags = SubobjectFlags;
	...
    Result = StaticConstructObject_Internal(Params);
    ...
    return Result;
}