How to pass function pointer of FTimeline.PlayFromStart

Development Programming & Scripting
1

I’m quite new to C++ programming in UE4 and I just can’t get the gist of this error. So a big part of my game logic is based on this DoOnce node from bp look-alike function. For starters, I tried to make it pretty general for maybe later reuse during development.
Here’s the plain logic of it:

//an alias for a function that returns void and has no parameters
using DoOnceFunc = void(*)();

//the DoOnce function that works with an optional parameter of type DoOnceFunc
void DoOnce(DoOnceFunc Func = 0) {
	static bool bDo = true;//initial state of the DoOnce
	if (Func != 0 && bDo) {
// if a func is pass in the optional parameter the bDo is checked and if both true the func is cold
		Func();
		bDo = false;//the purpose of the DoOnce is reached
	}
	else if(Func == 0) {
//otherwise is no function is pass by the optional parameter it means that the user desires to reset the DoOnce
		bDo = true;
	}
	
}

In simple Visual Studio project it all worked pretty smoothly. Now I want to implement it in my character class. I read through Rama’s Function Pointers article and followed through with the code:

  • in the character.h:

typedef void (AMain_Chr::*FunctionPtrType)(void); void DoOnce(FunctionPtrType Func = 0);

  • in the character.cpp:

void AMain_Chr::DoOnce(FunctionPtrType Func = 0) { static bool bDo = true; if (Func != 0 && bDo) { (this->*Func)(); bDo = false; } else if (Func == 0) { bDo = true; } }
And only portion of code where i use it is in an if statement where I check if character is standing still or not:

if (RLMovementInputFlag == 0) {
		GetCharacterMovement()->MaxWalkSpeed = 600;
		SprintBlend = 0;
		DoOnce();
	}
	else { DoOnce(AMain_Chr::LerpLagCam.PlayFromStart); }

The function passed in DoOnce() is a FTimeline.PlayFromStart. The error I get are:

  • error C3867: ‘FTimeline::PlayFromStart’: non-standard syntax; use ‘&’ to create a pointer to member
  • error C2572: ‘AMain_Chr::DoOnce’: redefinition of default argument: parameter 1
  • note: see declaration of ‘AMr_Clappy_Hands::DoOnce’

I don’t really understand the first error as I have also tried and pass in the function DoOnce(&AMain_Chr::LerpLagCam.PlayFromStart); or using the parameter void DoOnce(FunctionPtrType& Func = 0); even though it really doesn’t make sens. The second error I’m sure it has to do with me setting default value on the func parameter with 0 it being a pointer but default setting it with nullptr doesn’t work either. Having a default to the func is kind of the big point of the function without whitch it wouldn’t work right. The third error kind of gets on my nerve.
I tried using the UFUNCTION() macro and the following error was spit back: Error: Unrecognized type ‘FunctionPtrType’ - type must be a UCLASS, USTRUCT or UENUM.
I’m 99% sure it’s one of my newbish mistakes but I lost way to much time tinkering it. Plz kindly help. Oh, and also is there a tutorial for making a good function library? Sorry for bad english.