unreal-delegates-events

Delegates and Events - Unreal Engine 5.7

Delegate Types

• DECLARE_DELEGATE - Simple delegate without parameters
• DECLARE_DELEGATE_OneParam - Delegate with one parameter
• DECLARE_DELEGATE_Multicast - Multicast delegate (multiple listeners)
• DECLARE_DYNAMIC_DELEGATE - Delegate exposed to Blueprint
• DECLARE_DYNAMIC_MULTICAST_DELEGATE - Multicast exposed to Blueprint

Delegate Declaration

// In header
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnHealthChanged, float, NewHealth);

UCLASS()
class MYPROJECT2_API AMyActor : public AActor
{
    GENERATED_BODY()

public:
    UPROPERTY(BlueprintAssignable, Category = "Events")
    FOnHealthChanged OnHealthChanged;
};

Using Delegates

// Broadcast event
OnHealthChanged.Broadcast(NewHealth);

// Binding (C++)
OnHealthChanged.AddDynamic(this, &AMyActor::HandleHealthChanged);

// Unbinding
OnHealthChanged.RemoveDynamic(this, &AMyActor::HandleHealthChanged);

Blueprint Events

• Use BlueprintAssignable for events that can be assigned in Blueprint
• Use BlueprintCallable for functions that trigger events
• Dynamic events are slower but work with Blueprints

Best Practices

• Use delegates to decouple systems
• Prefer multicast delegates for events that multiple systems need to listen to
• ALWAYS unbind delegates when objects are destroyed
• Use dynamic delegates only when necessary to expose to Blueprint
• Static delegates are faster than dynamic ones