How to pass non-UFunction as parameter?

[pdenton (Leszek Górniak)]

Hello,

How to define a function parameter, so I can pass another function with it?

I’m trying to create a function template that will take another function (but not UFUNCTION) as parameter, like in BindUObject:

Delegate.BindUObject(this, &AMyTestActor::MyTestFunction);

I tried to simply recreate the way it’s done in BindUObject:

template <typename UserClass, typename... VarTypes>
inline void BindUObject(UserClass* InUserObject, typename TMemFunPtrType<false, UserClass, RetValType (ParamTypes..., VarTypes...)>::Type InFunc, VarTypes... Vars)

but this gives me “no instance of overloaded function matches the argument list” compile error when I try to pass another function in my function.

[Kehel18]

Hi! There are several things that can help you

• TFunctionRef is lambda-like template class. See TFunctionRef | Unreal Engine Documentation and https://www.orfeasel.com/understanding-lambda-expressions/
• FTimerUnifiedDelegate is used by Timers and can be created from almost all delegate subclasses, so you can use it. Examples can be found in Engine source: https://github.com/EpicGames/UnrealEngine/blob/1f94a613bdd33f487383ed1e8992d278bfe0920c/Engine/Source/Runtime/Engine/Public/TimerManager.h#L24
• You can also just use C++11 lambdas and function pointers, but I think that first two methods are much more consistent in Unreal Project, than this one

[pdenton (Leszek Górniak)]

OK, I managed to do this like that:

template <typename UserClass, typename... VarTypes>
static void MyFunction(UserClass* WorldContextObject, typename TMemFunPtrType<false, UserClass, void(VarTypes...)>::Type InFunc, VarTypes... Vars)
{
    FDelegate MyDelegate;
    MyDelegate.BindUObject(WorldContextObject, InFunc, Vars...);
    //...
}

The only restriction is the parameter function InFunc must have return type void (or other predefined type), but void is enough for me.

[pdenton (Leszek Górniak)]

Thanks, I ended up using TMemFunPtrType.