Download

error C2504: 'UInterface': base class undefined

C:\Users\Fang\Desktop\Engine\UnrealEngine_4.12.5\Engine\Source\Runtime\Engine\Classes\Interfaces/Interface_CollisionDataProvider.h(66): error C2504: ‘UInterface’: base class undefined

Any ideas why?
My module has two components. One inherits from BillboardComponent, the other from SkeletalMeshComponent.