C++ Interface FScriptInterface::SetObject Compile time Error

Development Programming & Scripting UI
, , , ,
1

I have an interface that I created by following the guide lines of the Interface article on the wiki called IInteractableActorInterface.

https://wiki.unrealengine.com/Interfaces_in_C%2B%2B

I have a Pawn that holds a pointer that references a IInteractableActorInterface that they are currently looking at and when you press E something happends. However for the life of me I get a compile time error that makes no bloody sense.

/** 
* Class required to support Interface Casting within the Unreal Engine System.
*/
UINTERFACE(MinimalAPI)
class UInteractableActorInterface : public UInterface
{
	GENERATED_UINTERFACE_BODY()
};


/** 
* InteractableActorInterface is an interface implemented by all objects within the game world
* that can be interacted with by a Pawn and Player.
*/
class IInteractableActorInterface
{
	GENERATED_IINTERFACE_BODY()

	/** 
	* Performs interaction on the object and supplies the instigator who triggered the action.
	*/
	virtual void Interact(APawn * instigator) = 0;

	/** 
	* Sets the proper properties for the instigator to alert the player or AI 
	* that the item is available for interaction.
	*/
	virtual void PrepareInteraction(APawn * instigator) = 0;

	/** 
	* Get a string that displays the interaction message.
	*/
	virtual FText GetInteractionMessage() = 0;
};

class AMyCharacter
{
// standard stuff here
private:
IInteractableActorInterface * interactableActor;

public:
IInteractableActorInterface * GetInteractableActor();
void SetInteractableActor(IInteractableActorInterface * interactableActor);
};

Error 7 error C2664: ‘void
FScriptInterface::SetObject(UObject
*)’ : cannot convert argument 1 from ‘IInteractableActorInterface *’ to
'UObject
*'InteractableActorInterface.cpp C:\Program
Files\Unreal
Engine\4.4\Engine\Source\Runtime\CoreUObject\Public\UObject\ScriptInterface.h 144 1

Now this error ONLY occurs if I use a pointer of the type of the interface, if I switch it to a hard coded type all is peachy…

class AMyCharacter
{
// standard stuff here
private:
APickup * interactableActor;

public:
APickup * GetInteractableActor();
void SetInteractableActor(APickup * interactableActor);
}

I have even commented out any locations where a InterfaceCast(object) is performed and still I get this error.

Digging through the Output I find:

C:\Program Files\Unreal Engine\4.4\Engine\Source\Runtime\CoreUObject\Public\UObject\ScriptInterface.h(144): error C2664: 'void FScriptInterface::SetObject(UObject *)' : cannot convert argument 1 from 'IInteractableActorInterface *' to 'UObject *'
1>          Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
1>          F:\Projects\UE4\Vishnu\Source\MyGame\Classes\Player\MyGameCharacter.h(16) : see reference to function template instantiation 'InterfaceType &TScriptInterface<InterfaceType>::operator =<IInteractableActorInterface>(UObjectType *)' being compiled
1>          with
1>          [
1>              InterfaceType=IInteractableActorInterface
1>  ,            UObjectType=IInteractableActorInterface
1>          ]
1>          F:\Projects\UE4\Game\Source\MyGame\Classes\Player\MyGameCharacter.h(16) : see reference to function template instantiation 'InterfaceType &TScriptInterface<InterfaceType>::operator =<IInteractableActorInterface>(UObjectType *)' being compiled
1>          with
1>          [
1>              InterfaceType=IInteractableActorInterface
1>  ,            UObjectType=IInteractableActorInterface
1>          ]

I don’t think I need to say it… but having to use a hard coded type defeats the purpose of trying to use an interface… any suggestions on what this error means would be highly welcome…

EDIT:
Clarification of Subject header… wrote this late at night and was tired.

2

Okay so the problem comes down to the fact that my function within my class was declared as a UFUNCTION() a detail I left out in my initial description of the problem.

UFunction(BlueprintCallable, Category=MyFunctions)
IInteractableActorInterface * MyGetFunction();

The solution to this is to change the definition of my function to

UFunction(BlueprintCallable, Category=MyFunctions)
UObject * MyGetFunction();

This fixed the problem and all is working.

Note: My actual solution was to change
the return type ot AActor* because I
know my interface will always be
applied to an actor object, but
UObject* is the base object you can
utilize.