Using the meta specifier MustImplement will cause the associated dropdown to only list classes/blueprints that implement the provided interface. If a blueprint has not been opened/loaded in the editor it does not appear in the dropdown selection

Ex: right click & Create Child Blueprint class

Opening the blueprint or right clicking on it will add it to the dropdown

No, same behavior occurs in 4.16.3

Steps to Reproduce
  1. Open UE4 Editor (any project)
  2. Add code classes based on ActorComponent (MyActorComp)
  3. Add the following to MyActorComp.h
    	UPROPERTY(EditAnywhere, meta = (MustImplement = "MyInterface"))
    		TSubclassOf<AActor> UsingMustImplement;
  4. Right click in Solution Explorer on the folder "ProjectName/Source/ProjectName" and select Add->New Item
  5. Create a Header File called MyInterface
  6. Add the following to MyInterface.h
    #include "MyInterface.generated.h"
    class UMyInterface : public UInterface
    class IMyInterface
    	/** React to a trigger volume activating this object. Return true if the reaction succeeds. */
    	UFUNCTION(BlueprintCallable, BlueprintImplementableEvent, Category = "Trigger Reaction")
    		bool ReactToTrigger() const;
  7. Compile
  8. In the editor, create a blueprint based on Actor (ParentBP)
  9. In the class settings, add MyInterface as an interface
  10. In the content browser right click on the blueprint to create a child blueprint (ChildBP)
  11. Add an empty actor to the viewport
  12. Add MyActorComp to the empty actor
  13. Save everything and restart the editor
  14. Select MyActorComp on the empty actor and expand the Using Must Implement dropdwon

ParentBP will show up in the dropdown list but ChildBP doesn't. Opening ChildBP or right clicking on it will cause it to show in the list

Blueprints with the given interface appear in the dropdown by default.

Have Comments or More Details?

There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-51321 in the post.

Login to Vote

Won't Fix
ComponentUE - Gameplay - Blueprint
Affects Versions4.
CreatedOct 16, 2017
ResolvedAug 18, 2021
UpdatedAug 18, 2021