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UE5.5目前使用FWorldPartitionActorDescInstance来管理world partition下的actor信息和逻辑操作，原来的FWorldPartitionActorDesc仅储存数据

FWorldPartitionActorDescInstance::GetActor函数不会触发加载，仅用于获取已加载或处于异步加载状态的actor，但如果actor处于异步加载状态时，会触发FWorldPartitionActorDescInstance::FlushAsyncLoad等待加载完成

UE5.5删除了FWorldPartitionActorDescInstance::Load接口并将FWorldPartitionActorDesc::Load设为空函数，仅在private内提供了异步加载接口，理由如下

• World Partition Actor Descriptors:
• Make loading functions private to make sure all code requesting actors loading state changes in the editor goes through the loading contexts.
• Actor descriptors can now load async when using the deferred context, in preparation of editor async loading through a new async context.

因此外部无法直接通过FWorldPartitionActorDescInstance加载Actor，目前UE提供了两种加载接口FWorldPartitionLoadingContext::FImmediate和FWorldPartitionLoadingContext::FDeferred，分别代表同步和异步加载

UE5.5可通过void FWorldPartitionLoadingContext::LoadAndRegisterActor(FWorldPartitionActorDescInstance* InActorDescInstance)直接加载actor，其实现如下

• void FWorldPartitionLoadingContext::LoadAndRegisterActor(FWorldPartitionActorDescInstance* InActorDescInstance)
  {
  check(!InActorDescInstance->bIsRegisteringOrUnregistering);
  InActorDescInstance->bIsRegisteringOrUnregistering = true;
  
  ActiveContext->RegisterActor(InActorDescInstance);
  }

• 其中默认情况下，采用同步加载:

• FWorldPartitionLoadingContext::FImmediate FWorldPartitionLoadingContext::DefaultContext;
  FWorldPartitionLoadingContext::IContext* FWorldPartitionLoadingContext::ActiveContext = &DefaultContext;

UE在此基础上封装了类型typedef TWorldPartitionHandle<FWorldPartitionReferenceImpl> FWorldPartitionReference;，用于记录actor引用计数，并且可以根据引用计数加载和卸载actor

• /**
  * FWorldPartitionReference will increment/decrement the hard reference count on the actor descriptor.
  * This will trigger actor loading/unloading when the hard reference counts gets to one/zero.
  */

同时UE还提供了typedef TWorldPartitionHandle<FWorldPartitionHandleImpl> FWorldPartitionHandle;类型仅用于记录引用计数

• /**
  * FWorldPartitionHandle will increment/decrement the soft reference count on the actor descriptor.
  * This won't trigger any loading, but will prevent cleanup of the actor descriptor when destroying an
  * actor in the editor.
  */
  typedef TWorldPartitionHandle FWorldPartitionHandle;

因此可以通过FWorldPartitionReference ActorReference(WorldPartition, ActorDesc->GetGuid());来加载actor，在其构造函数中会记录引用计数，并触发加载任务，其内部也是调用FWorldPartitionLoadingContext::LoadAndRegisterActor实现的