Custom logging doesn't compile

Development Programming & Scripting C++
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1

Hi!

I’m using Unreal 5.2.1 with C++ in a project called LineTraceProject.

I want to add custom logging, so I have added this to LineTraceProject.h:


// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "CoreMinimal.h"

DECLARE_LOG_CATEGORY_EXTERN(LogCustom, Log, All);

And this to LineTraceProject.cpp:

// Copyright Epic Games, Inc. All Rights Reserved.

#include "LineTraceProject.h"
#include "Modules/ModuleManager.h"

IMPLEMENT_PRIMARY_GAME_MODULE( FDefaultGameModuleImpl, LineTraceProject, "LineTraceProject" );

DEFINE_LOG_CATEGORY(LogCustom);

But, when I use it to the LineTraceProjectCharacter.cpp file:

UE_LOG(LogCustom, Log, TEXT("Tracing line: %s to %s"), *TraceStart.ToCompactString(), *TraceEnd.ToCompactString());

I get the following compiler error:

LineTraceProjectCharacter.cpp(126): error C2065: ‘LogCustom’: identifier not declared

Do I need to add #include "LineTraceProject.h" in LineTraceProjectCharacter.cpp?

I thought that it’s not necessary add the LineTraceProject.h file on each file that use the custom log.

2

At the top of your header add

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Character.h"
#include "LineTraceProjectCharacter.generated.h"

DECLARE_LOG_CATEGORY_EXTERN(LogCustom, Log, All);

at the cpp

// Fill out your copyright notice in the Description page of Project Settings.


#include "LineTraceProjectCharacter.h"

// at top of code
DEFINE_LOG_CATEGORY(LogCustom);

then

UE_LOG(LogCustom, Log, TEXT("Tracing line: %s to %s"), *TraceStart.ToCompactString(), *TraceEnd.ToCompactString());

should compile

3

Thanks, but I want to use globally. This is why I have defined it in LineTraceProject.h.

4

Do what the engine does:
define a custom class to hold your globals (Unreal has CoreGlobals h and cpp)

In your custom globals cpp file add your DEFINE_LOG_CATEGORY(LogCustom); and include it in your header where you want to use it.

Maybe this could be done in a subsystem? I’ll give it a look over.

==================================

Edit: found the perfect middle-ground:

Create 2 files

  • the global class header file
  • the global class header file

I called my files MyGlobal.h & MyGlobal.cpp

inside of the header put:

#pragma once

#include "CoreMinimal.h"

DECLARE_LOG_CATEGORY_EXTERN(LogCustom, Log, All);

inside of the CPP

#include "MyGlobal.h"  // your header name here

DEFINE_LOG_CATEGORY(LogCustom);

Then inside of your main file in this case
LineTraceProject.h because the project name is LineTraceProject


#pragma once

#include "CoreMinimal.h"
#include "MyGlobal.h"  // <== your global files header

Now you can use the custom log globally within the project

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