Using EventDispatcher from C++

Every Blueprint node is a static function on UEventManager, so the C++ API matches the Blueprint API.

Setup

Add the module to your .Build.cs:

PrivateDependencyModuleNames.AddRange(new string[] { "EventDispatcher" });

Include the header:

#include "EventDispatcherManager.h"

Callbacks must be UFUNCTIONs

The callbacks are dynamic delegates, so the function you bind must be a UFUNCTION(). Lambdas and raw function pointers are not supported.

UCLASS()
class AScoreDisplay : public AActor
{
	GENERATED_BODY()

protected:
	virtual void BeginPlay() override;
	virtual void EndPlay(const EEndPlayReason::Type EndPlayReason) override;

	UFUNCTION()
	void OnScoreChanged(int32 NewScore);

	UPROPERTY(EditAnywhere)
	UEventIdentifier* ScoreChangedEvent;
};

Registering

void AScoreDisplay::BeginPlay()
{
	Super::BeginPlay();

	FIntEventDelegate Callback;
	Callback.BindDynamic(this, &AScoreDisplay::OnScoreChanged);

	UEventManager::RegisterIntEvent(this, ScoreChangedEvent, Callback);
}

The first argument is the world context and also the object that Optional Target and Unregister … By Object match against.

For a named event:

UEventManager::RegisterIntEventName(this, TEXT("ScoreChanged"), Callback);

Invoking

UEventManager::InvokeIntEvent(this, nullptr, ScoreChangedEvent, 42);
UEventManager::InvokeIntEventName(this, nullptr, TEXT("ScoreChanged"), 42);

The second argument is the optional target. Pass nullptr to reach every listener.

Unregistering

void AScoreDisplay::EndPlay(const EEndPlayReason::Type EndPlayReason)
{
	UEventManager::UnregisterEventByObject(this, ScoreChangedEvent, this);

	Super::EndPlay(EndPlayReason);
}

Delegate types

Event type	Delegate	Callback signature
Simple	FSimpleEventDelegate	void()
Payload	FPayloadEventDelegate	void(UObject* Payload)
String	FStringEventDelegate	void(const FString& String)
Int	FIntEventDelegate	void(int32 Value)
Float	FFloatEventDelegate	void(float Value)
Bool	FBoolEventDelegate	void(bool Value)
Vector	FVectorEventDelegate	void(const FVector& Data)
String + Float	FStringFloatEventDelegate	void(const FStringFloat& Data)
String + Int	FStringIntEventDelegate	void(const FStringInt& Data)

Inspecting the manager

The manager is a Game Instance subsystem:

UEventManager* Manager = GetGameInstance()->GetSubsystem<UEventManager>();
const int32 NumListeners = Manager->GetNumRegisteredEvents();
const int32 NumPending = Manager->GetNumQueuedEvents();