function 'FArchive &operator <<(FArchive &,AMainCharacter *&)' already has a body

I have followed this tutorial from Rama:

A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums,Read%26_Write_Any_Data_to_Compressed_Binary_Files

I want to override the operator << in a class (MainCharacter) to store a public Int32 value that AMainCharacter has, called TestIntValue;

With trial and error, I got it working, but I don’t know what did I change that it doesn’t work any more.

My code is simple:


    void AMyPlayerController::SaveLoadData(FArchive& Ar, int32& SaveDataInt32, FVector& SaveDataVector, AMainCharacter*& MainCharacter)
    	Ar << SaveDataInt32;
    	Ar << SaveDataVector;
    	Ar << MainCharacter;

SaveLoadLib.h Full code:

#pragma once
#include "Object.h"
#include "Characters/MainCharacter.h"
FORCEINLINE FArchive& operator<<(FArchive& Ar, AMainCharacter*& MC) 
	Ar << MC->TestIntValue;
	return Ar;


#include "Engine.h"
#include "SaveLoadLib.h"
#include "Kismet/GameplayStatics.h"

It doesn’t compile. The error is:

*1>c:\unreal projects\MyProject\source\myproject\SaveLoadLib.h(8): error C2084: function 'FArchive &operator <<(FArchive &,AMainCharacter &)’ already has a body

1> c:\unreal projects\MyProject\source\myproject\Characters/MainCharacter.h(15): note: see previous definition of '<<'

I am more interested in understanding how this works than just getting it working or having a walkaround. I think I undestand the following points:

  1. Unreal uses the operator << to read
    and write.
  2. The order is important, so loading and saving must be executed in the same order.
  3. FORCEINLINE is a requirement for operator overloads if you want to be able to easily define them in a way that the UE4 compiler will like even when you have code split across multiple .cpp chunks (from Rama’s tutorial)

I want to serialize and save to disk some of the Actors and Structs that are in the Level.

Should I instead implement a function in the actors that I’m interested to save like:

//Class that Implements Interface MySaveLoad 

void MyObject::SaveLoad(FArchive& Ar)
	Ar << Int32Value;
	Ar << AnotherPrimitiveValue;
	ChildObject->SaveLoad(Ar);//this might lead to circular dependencies


Is there a better/more standardize way to do this? Is there any Design Patterns/Best Practice that I can follow? What happens with the private members of Unreal Class (Like AActor) that I’m extending from?

Please Help!!



Just in case anybody is interested, this is how I solved it:

class TEST_API ASaveActor : public AActor


	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = Test)
	int32 TestIntValue = 12;

	friend FArchive& operator<<(FArchive& Ar, ASaveActor& SObj)
		Ar << SObj.TestIntValue;    
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