UE4中dynamic create component及ChildActorComponent未解析符号 问题

1.dynamic create component

正常方法添加组件方法是

On Character.h I add a USpringArm and UChildActor component :

UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = InventoryCamera)
TSubobjectPtr<class USpringArmComponent> InventorySpringArm;

UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = InventoryCamera)
TSubobjectPtr<class UChildActorComponent> InventoryCamera;

On Character.cpp Constructor I add this code to Initialize those Actors :

InventorySpringArm = PCIP.CreateDefaultSubobject<USpringArmComponent>(this, TEXT("InventorySpringArm"));
InventorySpringArm->AttachTo(CapsuleComponent);
InventorySpringArm->bUseControllerViewRotation = false;

InventoryCamera = PCIP.CreateDefaultSubobject<UChildActorComponent>(this, TEXT("InventoryCamera"));
InventoryCamera->ChildActorClass = UCameraComponent::StaticClass();
InventoryCamera->CreateChildActor(); // <-- this code throws a Compile Error下面会说道childactor这么生成会有问题的
InventoryCamera->AttachTo(InventorySpringArm);ps:也有的版本PCIP写成ObjectInitiallizer
但这个方法问题在于CreateDefaultSubobject 只能在构造函数里面调用

因此想要动态生成组件方法是：

Creating and Registering Components During Runtime

Code:

//in some AActor class

void AYourActor::CreateComponent(UClass* CompClass,const FVector& Location, const FRotator& Rotation, const FName& AttachSocket=NAME_None)
{
FName YourObjectName("Hiiii");

//CompClass can be a BP
UPrimitiveComponent* NewComp = ConstructObject<UPrimitiveComponent>( CompClass, this, YourObjectName);
if(!NewComp)
{
return NULL;
}
//~~~~~~~~~~~~~

NewComp->RegisterComponent();        //You must ConstructObject with a valid Outer that has world, see above
NewComp->SetWorldLocation(Location);
NewComp->SetWorldRotation(Rotation);
NewComp->AttachTo(GetRootComponent(),SocketName,EAttachLocation::KeepWorldPosition);
//could use different than Root Comp

参考：

1.https://forums.unrealengine.com/showthread.php?52410-What-is-the-correct-way-to-create-and-add-components-at-runtime

2.ChildActorComponent的createChildActor方法使用，未解析外部引用

查看ChildActorComponent.h的源代码就知道

中间有

//start interface

......

//end interface

的注释，createChildActor方法在下面，并没有暴露出来

这里要使用childActorComponent->OnComponentCreated();方法

它会内部调用createChildActor方法

参考：

1.https://answers.unrealengine.com/questions/90283/unresolved-externals-error-with-uchildactorcompone.html

2.https://answers.unrealengine.com/questions/101002/uchildcomponentactor-createchildactor-compile-erro.html