《UE4游戏开发》之 《UE4 GC编程》

1. TWeakObjectPtr
   1.1 声明：TWeakObjectPtr Owner;

class TESTENGINE_API FTestGC : public FGCObject
{
public:
	TWeakObjectPtr<UObject> Owner;
	USkeletalMeshComponent* SkeletalMeshComponent;
	FTestGC();
public:
	void InitComponent();
	void PrintInfo();
protected:
// 测试结果：当UObject的outer被销毁时，GC也会销毁对应的UObject，
//该函数的操作，无法确保UObject不被销毁
	virtual void AddReferencedObjects(FReferenceCollector& Collector) override;
};

1.2 赋值：

void ATestEngineGameModeBase::BeginPlay()
{
	Super::BeginPlay();
	TestGC = MakeShared<FTestGC>();
	TestGC->Owner = GetWorld();
	TestGC->InitComponent();
}
void ATestEngineGameModeBase::TestGCSpawn()
{
	UWorld* World = GetWorld();
	
	TestGCActor = World->SpawnActor<AActor>(AActor::StaticClass());
	FAttachmentTransformRules AttachmentRules = FAttachmentTransformRules(EAttachmentRule::KeepRelative,false);
	TestGC->SkeletalMeshComponent->AttachToComponent(TestGCActor->GetRootComponent(), AttachmentRules);
	TestGC->Owner = TestGCActor;
}
void FTestGC::PrintInfo()
{
	UObject* Outer = SkeletalMeshComponent->GetOuter();
	if (Owner.IsValid())
	{
		UE_LOG(LogTemp, Log, TEXT("FTestGC::PrintInfo:Owner: %s"), *Owner->GetFName().ToString())
	}
	if (Outer)
	{
		UE_LOG(LogTemp, Log, TEXT("FTestGC::PrintInfo:SkeletalMeshComponent.Outer: %s"), *Outer->GetFName().ToString())
	}
}
void ATestEngineGameModeBase::TestGCInfo()
{
	if (TestGCActor)
	{
		UE_LOG(LogTemp,Log, TEXT("ATestEngineGameModeBase::TestGCInfo:TestActor: %s"),*TestGCActor->GetFName().ToString());
	}
	TestGC->PrintInfo();
}
void FTestGC::AddReferencedObjects(FReferenceCollector& Collector)
{
	Collector.AddReferencedObject(SkeletalMeshComponent);
}

1.3 赋值含义：可以通过Owner获取指向TestGCActor的指针，但是不会增加引用计数；即TestGCActor的销毁，与Owner没有关系
1.4 如果Owner再次赋值：与普通指针一样，指针指向的内容为新的对象；BeginPlay中，Owner指向World，在TestGCSpawn中指向TestGCActor

2. 验证通过继承FGCObject的类管理【创建】UObject的类的对象，即使将UObject对象加入GGCObjectReferencer，当UObject的outer被销毁时，GC也会销毁对应的UObject