Object Lifecycle Events

These are the object lifecycle events which can run blocks. All object-specific events use the On.* prefix. The table shows how they map to object lifecycle events in the most popular game engines:

LunyScript	Unity	Godot	Unreal
On.Created	Awake	_init	InitializeComponent
On.Ready	Start	_ready	BeginPlay
On.Enabled	OnEnable	_enter_tree	OnComponentActivated
On.Disabled	OnDisable	_exit_tree	OnComponentDeactivated
On.Heartbeat	FixedUpdate	_physics_process	TickComponent
On.FrameUpdate	Update	_process	TickComponent
On.FrameLateUpdate	LateUpdate	N/A	TickComponent
On.Destroyed	OnDestroy	N/A (manual)	UninitializeComponent
On.Collision(2D).Started	OnCollisionEnter(2D)	body_entered	OnComponentHit
On.Collision(2D).Touching	OnCollisionStay(2D)	N/A (manual)	N/A (manual)
On.Collision(2D).Ended	OnCollisionExit(2D)	body_exited	N/A (manual)
On.Trigger(2D).Entered	OnTriggerEnter(2D)	area_entered	OnComponentBeginOverlap
On.Trigger(2D).Overlapping	OnTriggerStay(2D)	N/A (manual)	N/A (manual)
On.Trigger(2D).Exited	OnTriggerExit(2D)	area_exited	OnComponentEndOverlap

Notable exceptions using nouns/adjectives instead of following the past tense -ed and participle -ing rules:

• Frame events: On.Heartbeat, On.FrameUpdate
• The once-only event: On.Ready

This is because On.Heartbeating, On.FrameUpdating and On.Readied seemed rather odd.

Note

Why "heartbeat"? I find that's where every engine has issues: FixedUpdate .. uh, what is 'fixed' here? Is Update() broken?? And _physics_process is too narrow and misleading: it's not (just) about physics.

The concept of a heartbeat is simple and relatable: It happens at a steady rate, most of the time. But it can also "skip a beat" (may not run every frame), or have an "extra beat" or even "race" (run multiple times per frame to catch up).