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Lifecycle and Events

This page compares Unity lifecycle methods with the Unreal equivalents you will use most.

Lifecycle Comparison

Unity Unreal Notes
Awake Constructor Constructor sets defaults and creates default subobjects. World state may not be ready yet.
Start BeginPlay Safe place for gameplay startup logic.
Update Tick Runs every frame if ticking is enabled.
OnDestroy EndPlay / destruction flow EndPlay tells you why the actor is ending play.
Input method setup SetupPlayerInputComponent Common on APawn and ACharacter.

Constructor

Unity Version

Unity developers often put setup in Awake.

Unreal Version

The constructor is for:

  • default values
  • component creation
  • configuration that should exist before play

Do not rely on other world objects being ready here.

BeginPlay

BeginPlay is the common place for runtime startup logic.

void AMyActor::BeginPlay()
{
    Super::BeginPlay();
}

Tick

Use Tick only when the object truly needs per-frame work.

AMyActor::AMyActor()
{
    PrimaryActorTick.bCanEverTick = true;
}

void AMyActor::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);
}

Frequent ticking is easy to overuse. See Profiling and Optimisation.

EndPlay

EndPlay is often clearer than thinking only in terms of destruction.

void AMyActor::EndPlay(const EEndPlayReason::Type EndPlayReason)
{
    Super::EndPlay(EndPlayReason);
}

SetupPlayerInputComponent

Characters and pawns commonly bind input here.

void AMyCharacter::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent)
{
    Super::SetupPlayerInputComponent(PlayerInputComponent);
}

With Enhanced Input, you usually add mapping contexts elsewhere as well. See Input.

Delegates

Delegates are Unreal's event callback system.

Single-cast Delegate

DECLARE_DELEGATE(FOnReloaded);

Multicast Delegate

DECLARE_MULTICAST_DELEGATE(FOnReloadedMulti);

Dynamic Multicast Delegate

Use this when Blueprints need to bind to the event.

DECLARE_DYNAMIC_MULTICAST_DELEGATE(FOnHealthChanged);

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

Common Mistake

A common trap is treating the constructor like Start. In Unreal, constructor code is often about defaults and component setup, not world-dependent gameplay logic.