Using C++ to Bind to a Delegate in Unreal Engine 5

Software Versions: Unreal Engine 5.5.0 | Rider 2024.2.7

Project Name: MyProject

Building off a couple of previous posts (Dispatchers and Delegates) I wanted to go through Epic's documentation and bind a delegate with C++ using their LogWriter example.

I started by creating a non-UObject class, so just a regular C++ class, and called it FLogWriter. The class is very simple, it declares a one parameter delegate and one WriteLog function that accepts one FString parameter. The WriteLog function simply writes to the console.

FLogWriter.h

#pragma once

DECLARE_DELEGATE_OneParam(FStringDelegate, FString);

class FLogWriter
{
public:
	void WriteToLog(FString MyText);
};

FLogWriter.cpp

#include "FLogWriter.h"

void FLogWriter::WriteToLog(FString MyText)
{
	UE_LOG(LogTemp, Warning, TEXT("Log Writer Delegate Text: %s"), *MyText);
}

Next, I created a new actor class and called it MyDelegateBindActor. The header file imports the FLogWriter class to declare a delegate signature. Then inside the constructor we declare a shared reference, TSharedRef, to the FLogWriter class and use BindRaw to bind to the WriteToLog function.

Finally, for a simple example in BeginPlay we use ExecuteIfBound to call the function while passing in an argument.

When testing I Couldn't get BindSP to work with IsBound or ExecuteIfBound. So Instead I used BindRaw

MyDelegateBindActor.h

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "FLogWriter.h"
#include "MyDelegateBindActor.generated.h"

UCLASS()
class MYPROJECT_API AMyDelegateBindActor : public AActor
{
	GENERATED_BODY()

public:
	// Sets default values for this actor's properties
	AMyDelegateBindActor();

protected:
	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

public:
	FStringDelegate WriteToLogDelegate;
};

MyDelegateBindActor.cpp

#include "MyDelegateBindActor.h"

// Sets default values
AMyDelegateBindActor::AMyDelegateBindActor()
{
	TSharedRef<FLogWriter> LogWriter(new FLogWriter());
	
	WriteToLogDelegate.BindRaw(&LogWriter.Get(), &FLogWriter::WriteToLog);
}

// Called when the game starts or when spawned
void AMyDelegateBindActor::BeginPlay()
{
	Super::BeginPlay();

	WriteToLogDelegate.ExecuteIfBound(TEXT("Delegate Exectuing if Bound"));
}

With the new class compiled I create a new BP actor that inherits from MyDelegateBindActor and added a basic cylinder mesh and dragged it into the scene. On BeginPlay a message appears in the console.