TSubClassOf with Interfaces isn't working

Development Programming & Scripting UI
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1

I have the following c++ interface

UINTERFACE(Blueprintable)
class UActionInterface : public UInterface
{
	GENERATED_UINTERFACE_BODY()
};

class IActionInterface
{
	GENERATED_IINTERFACE_BODY()
};

I am then implementing this interface via my c++ weapon class

UCLASS(ABSTRACT, Blueprintable)
class FPSGAME_API AFPSWeapon : public AActor, public IActionInterface

I then create a Blueprint from this FPSWeapon and add the ActionInterface under the Interfaces section.

75580-shotgun.png
75580-shotgun.png1595×513 151 KB

My Character c++ class has the following property

// Default Inventory List
UPROPERTY(EditDefaultsOnly, Category = Inventory)
TArray<TSubclassOf<IActionInterface>> DefaultInventoryClasses;

But now in the editor I get nothing for this dropdown instead of the shotgun bp like I would expect.

75591-nothing.png
75591-nothing.png1382×210 82.6 KB

Does anyone know why my Shotgun BP doesn’t show up here?

Thanks!

2

Interfaces are not identify as UClass* so TSubclassOf (which work the same as UClass* just limiting the UClass selection i editor) won’t work either.

Use this insted

TScriptInterface<IActionInterface>
3

So I can’t limit the TSubclassOf dropdown to only my interface?

4

use UActionInterface insted of UInterface, but keep in mind those are like class identificators, not object pointers and i don’t know if you can do anything with those in blueprints.

5

Yeah even with TArray< TSubclassOf< UActionInterface > > DefaultInventoryClasses; I still get nothing in the dropdown box.

6

Ok i think i get it now you want list of objects that implements interface, i dont think there is anyway to do so. If you can find node in engine that is example of that i can find how it was made for you

7

Yeah, I am expecting to see my Shotgun BP in the dropdown box since it implements the interface. Is that not reasonable?

8

HA! Found it ^^ I digged a little in UHT code and find TScriptInterface

Try using I class if this wont work try using U class of interface

9

USe I class i found example in engine source code, i modified anwser, tell me if it works

10

When I use that I don’t get a dropdown at all.

75593-nodropdown.png

11

I was able to get the following working. But now I’m interested in TScriptInterface.

UPROPERTY(EditDefaultsOnly, meta = (MustImplement = "ActionInterface"))
TArray<TSubclassOf<UObject>> DefaultInventoryClasses;
1 Like
12

Ah ok :slight_smile: Well then as you anwser to your quastion yourself i will turn it in to anwser and mark as resulved. I guess that template i told you is not supported by blueprints

13

Thank you!

14

What is that a TArray of?

Should it be UObjects:

TArray<UObject*> DefaultInventoryClasses;
15

Sorry not sure how that got chopped off before. I’ve edited my answer with how I have it.

16

Both of these worked for me:

UPROPERTY(EditDefaultsOnly, config, NoClear, Category="SomeCategory", meta=( MustImplement=SomeInterface ))
TSubclassOf<UObject> SomeVariable;

UPROPERTY(EditDefaultsOnly, config, NoClear, Category="SomeCategory", meta=( MustImplement=SomeInterface ))
UClass* SomeVariable;

I did this in a UDeveloperSettings so I had more restrictions about what kinds of variables were allowed (hence config and NoClear).