Passing a UStruct to a BlueprintImplementableEvent in 4.15

[MrBurgerAt]

I seem to be unable to pass a custom UStruct to a BlueprintImplementableEvent in 4.15, even in a clean project. To do this, I set up a custom player controller that overrides BeginPlay() and calls two functions, defined as such in MyPlayerController.h:

USTRUCT(BlueprintType)
struct FMyStruct
{
	GENERATED_USTRUCT_BODY()

	int32 TestInt;
	FText TestText;
};


UCLASS()
class MYPROJECT_API AMyPlayerController : public APlayerController
{
	GENERATED_BODY()

public:

	virtual void BeginPlay() override;
	
	UFUNCTION(BlueprintImplementableEvent)
		void BP_LoadTArray(const TArray<FMyStruct> &MyStructArray);

	UFUNCTION(Blueprintimplementableevent)
		void BP_LoadStruct(const FMyStruct& MyStruct);
};

MyPlayerController.cpp is pretty simple:

void AMyPlayerController::BeginPlay()
{
	Super::BeginPlay();

	FMyStruct NewStruct;
	NewStruct.TestInt = -1;
	NewStruct.TestText = FText::FromString("test");

	TArray<FMyStruct> MyStructArray;
	MyStructArray.Add(NewStruct);

	// testing whether we can pass a struct array by const ref
	// is it empty?
	if (MyStructArray.Num() > 0)
	{
		GEngine->AddOnScreenDebugMessage(-1, 10.f, FColor::Red, MyStructArray[0].TestText.ToString());
	}

	BP_LoadTArray(MyStructArray);

	// testing whether we can pass a struct itself
	// is it empty?
	GEngine->AddOnScreenDebugMessage(-1, 10.f, FColor::Red, NewStruct.TestText.ToString());

	BP_LoadStruct(NewStruct);
}

Then, I made a Blueprint Child class of MyPlayerController, which implemented the previously defined Functions/Events, just to place some BreakPoints and check whether the events have data in the passed Structs. Simply put, they don’t. Does anyone know why?

[Wurmloch83]

Have you defined your Blueprint class as PlayerControllerClass in your game mode constructor?

[MrBurgerAt]

I have added the tag: UPROPERTY(BlueprintReadWrite) to the TestInt and TestText in FMyStruct. This did however not solve the problem

[MrBurgerAt]

Of course. The program even stops at the breakpoints as expected, the only thing that is missing are the contents of the UStructs.

When I do the same project in 4.14, these are available.

[Wurmloch83]

Could this possibly be a debugger bug? have you tried actually printing the contents of the struct to screen?
Something possible similar came up today here: https://answers.unrealengine.com/questions/565219/maybe-found-a-bug-with-arrays-and-array-length-blu.html

[MrBurgerAt]

I feel incredibly stupid for this mistake, but the solution was quite simple all along. When I tried to print the contents, I noticed that I could not break the structs in Blueprint.

Adding a VisibleAnywhere to the UProperty Tag in FMyStruct solved the problem . The struct contents are visible now -.-