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BaseControl

Base class for all Flet controls and services.

Properties

  • data - Arbitrary data of any type.
  • key - A stable key used to preserve control identity across updates.
  • page - The page to which this control belongs to.
  • parent - The direct ancestor(parent) of this control.

Methods

  • before_event - Intercept an event before its handler is executed.
  • build - Called once during control initialization to define its child controls.
  • did_mount - Called after the control is mounted into the page tree.
  • get_data_channel - Resolve the [DataChannel] allocated on the Dart side for this widget.
  • is_isolated - Return whether this control is marked as isolated.
  • update - Request a UI update for this control.
  • will_unmount - Called before the control is removed from the page tree.

Properties​

dataclass-attributeinstance-attribute​

data: Any = skip_field()

Arbitrary data of any type.

keyclass-attributeinstance-attribute​

key: KeyValue | None = None

A stable key used to preserve control identity across updates.

pageproperty​

page: Page | BasePage

The page to which this control belongs to.

parentproperty​

parent: BaseControl | None

The direct ancestor(parent) of this control.

It defaults to None and will only have a value when this control is mounted (added to the page tree).

The Page control (which is the root of the tree) is an exception - it always has parent=None.

Methods​

before_event​

before_event(e: ControlEvent)

Intercept an event before its handler is executed.

Return False to cancel dispatch. Return True or None to continue normal event processing.

build​

build()

Called once during control initialization to define its child controls. page property is available/usable in this method.

did_mount​

did_mount()

Called after the control is mounted into the page tree.

Override to start resources that require an attached page, for example subscriptions, timers, or service listeners.

get_data_channel​

get_data_channel(channel_id: int)

Resolve the [DataChannel] allocated on the Dart side for this widget. Pattern:

on_data_channel_open: Optional[ft.EventHandler[DataChannelOpenEvent]] = None

def init(self): self.on_data_channel_open = self._on_open

def _on_open(self, e): self._channel = self.get_data_channel(e.channel_id)

Idempotent — the underlying Connection caches DataChannels by id, so repeated calls return the same instance. No error path: the id always comes from a framework-fired event, so by the time this runs the channel exists on both sides.

is_isolated​

is_isolated()

Return whether this control is marked as isolated.

Isolated controls are excluded from parent-driven update traversal and are expected to manage their own update boundaries.

update​

update() -> None

Request a UI update for this control.

Call after changing control state or properties. The control must be attached to a page and not marked as frozen.

will_unmount​

will_unmount()

Called before the control is removed from the page tree.

Override to dispose resources created in did_mount(), such as subscriptions, timers, or external handles.