Resolving Circular Dependency

Development Programming & Scripting C++
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1

Can anyone help me understand how this works? I am trying to implement the LastTakeHitInfo feature in my game. I was looking at the ShooterGame example to see how they did it. I am running into a circular dependency issue and I am not sure why the Shoot Game works and mine doesn’t.

ArenaCharacter.cpp

#include "ArenaTypes.h"
#include "ArenaDamageType.h"
#include "GameFramework/Character.h"
#include "ArenaCharacter.generated.h"

UCLASS(Abstract)
class AArenaCharacter : public ACharacter
{
	GENERATED_UCLASS_BODY()

    (...)

    /** Replicate where this pawn was last hit and damaged */
	UPROPERTY(Transient, ReplicatedUsing = OnRep_LastTakeHitInfo)
	struct FTakeHitInfo LastTakeHitInfo;

    (...)

}

Because ArenaCharacter implements “struct FTakeHitInfo LastTakeHitInfo” it needs to include #include “ArenaTypes.h”. There is a problem though

ArenaTypes.h

#include "Object.h"
#include "ArenaCharacter.h"
#include "GameFramework/DamageType.h"
#include "ArenaTypes.generated.h"

#pragma once

USTRUCT()
struct FTakeHitInfo
{
	GENERATED_USTRUCT_BODY()

        (...)

        /** Who hit us */
	    UPROPERTY()
	    TWeakObjectPtr<class AArenaCharacter> PawnInstigator;

        (...)

}

The pawn investigator needs to know about AArenaCharacter. If I don’t include #include “ArenaCharacter.h” I get the error: TWeakObjectPtr can only be constructed with Object types. But obviously when I add #include “ArenaCharacter.h” header it creates a circular dependency. This is how the Shoot game works. What am I missing?

2

Hi Ky,

Do you really have AArenaCharacter defined in ArenaCharacter.cpp file, as you have suggested? Any marked-up (i.e. UCLASS, USTRUCT etc.) types must be defined in a .h file of the same name as the type, but without the prefix - i.e. ArenaCharacter.h in your case - and in a Public, Private or Classes folder located underneath your module folder.

Steve

3

I figured it out. In the ShooterGame example in the ShooterGame.h they #include a header file called ShooterGameClasses.h this file contained a #include to every class in the project. Its is actually auto generated by the Unreal Engine. I looked in my project and found I too have a MyProjectClasses.h however mine was empty. You can’t add anything to that file since it is auto generated and will delete anything you add to it. I instead added all the includes into MyProject.h then I simple #include MyProject.h for every classes. This will insure no circular dependencies are created even when two classes refence each other.

2 Likes
4

Yes it is defined, I actually just figured out what the problem was, thanks though!

5

For me it also worked to set the default value in the constructor in the .cpp instead of directly in the .h file.

6

thank you so much.
Worked for me :slight_smile:

7

thank you so much.
Worked for me :slight_smile:

8

Hello, can you please help with that? I tried to use all includes in my project.h file and then I used include project.h in both header files. Can you please explain me with the example. Please help me out with this, I am stuck here as I cannot use forward declaration because I have to store reference of each other for further use.