Lifecycle

Lifecycle

Widgets have three lifecycle callbacks: mount, unmount and update.

mount

Fires after a widget is added to the tree via addChild. self.parent is already set when the handler runs.

widget:onMount(function(self)
    print("mounted, parent is", self.parent)
end)

To override in a subclass:

function MyWidget:mount()
    Widget.mount(self)  -- fires registered onMount handlers
    -- custom setup
end

unmount

Fires after a widget is removed from the tree via removeChild. self.parent is already nil when the handler runs but self.children, props, and reactive state are still intact.

widget:onUnmount(function(self)
    print("unmounted")
end)

To override in a subclass:

function MyWidget:unmount()
    Widget.unmount(self)  -- fires registered onUnmount handlers + cleans up reactive state
    -- custom teardown
end

update

Fires every frame via host:update(dt). dt is delta time in seconds.

local x = 0

widget:onUpdate(function(self, dt)
    x = x + 100 * dt
end)

To override in a subclass:

function MyWidget:update(dt)
    Widget.update(self, dt)  -- fires registered onUpdate handlers + propagates to children
    -- per-frame logic
end

Examples

Search lifecycle in the example browser.