Putting custom delegate definition in a header - Compile error.

Development Programming & Scripting C++
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1

Hi all…

I have a C++ class derived from UObject that implements various functionality. I’ll just call it UClass-A. In that header file, I had defined two custom delegates that were to be used in this class and another, I’ll call it UClass-B. All this was working fine. The other class could see and use the delegate types just fine.

However, I wanted to move the delegate definitions into a separate header file where the sole purpose of that header was to contain custom delegate definitions to be used across multiple classes in the underlying C++ framework.

I used Unreal to create a new C++ class based on UObject called CustomDelegates.h just for the purpose of having a location to define all my delegates. Once Unreal was done generating everything, I moved the delegate definitions from UMyClass and into this CustomDelegates.H file.

In CustomDelegates.H, I removed all the class reference stuff out of the header file just so that it was a pretty empty header with only the custom delegate definitions. I DID leave in the #includes that Unreal generated for me.

I went into UClass-A and UClass-B and ensured that both the header files had the proper include specifying CustomDelegates.H.

Not sure if this would make a difference but could be part of the problem I’m seeing, my inheritance looks like this…

UClass-A : UObject
UClass-B : AActor

And again, when I had the delegate definitions in UClass-A header, everything worked fine.

However, now that I moved the delegate definitions into CustomDelegates.H, UClass-B can’t find the delegates. I don’t get any type of error saying that the compiler can’t find CustomDelegates.h, rather, it just says that it can’t find the definition for my delegates.

No compile errors against UClass-A, only UClass-B. Seems odd that both classes could find and use these delegates when they were defined at the top of UClass-A.

Anyone have any thoughts on why this might be happening?

EDIT
So, I opened up CustomDelegates.h. I put the class definition back in the header. It sits below the delegate definitions and is as basic as can be…

UCLASS()
class MYPLUGIN_API CustomDelegates : public UObject
{
    GENERATED_BODY()
};

After putting this back in the header… Compiles great…
Does anyone know why that would need to be in there?

1 Like
2

Hi!

Is a problem only with UClass-B? UClass-A can use delegates when you move them to separate header?

Also, can you please share .h and .cpp files in question? Maybe this way it will be easier to spot a problem.

3

Mark your delegates as UDELEGATE()

UDELEGATE()
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnSomething, UObject*, SomeObject);

I know its old but I came here from Google so providing the answer for others who also come here from google.

If there is no USTRUCT(), UCLASS(), etc. in your delegate only header it won’t compile without UDELEGATE()