avoid_state_constructors

v0.4.0WarningFixConfigurableState Management

Flags State subclasses that have constructors with non-empty bodies or initializer lists. Initialization logic in State classes should live in initState(), not in the constructor, to respect the Flutter widget lifecycle.

Why use this rule

The State constructor runs before the framework has fully initialized the state object. At construction time, widget, context, and other framework-provided properties are not yet available. Placing logic in the constructor can lead to subtle bugs when that logic depends on the widget tree. Using initState() ensures all framework wiring is in place.

See also: State class | State.initState | Dart lint: no_logic_in_create_state

Don’t

class _BadWidget1State extends State<BadWidget1> {
  late String _data;

  // Constructor body should be empty — move logic to initState()
  _BadWidget1State() {
    _data = 'Hello';
  }

  @override
  Widget build(BuildContext context) => const SizedBox();
}

class _BadWidget2State extends State<BadWidget2> {
  final String _data;

  // Initializer list in State constructor — move logic to initState()
  _BadWidget2State() : _data = 'Hello';

  @override
  Widget build(BuildContext context) => const SizedBox();
}

Do

class _GoodWidgetState extends State<GoodWidget> {
  late String _data;

  @override
  void initState() {
    super.initState();
    _data = 'Hello';
  }

  @override
  Widget build(BuildContext context) => const SizedBox();
}

// Empty constructor is fine
class _GoodWidget2State extends State<GoodWidget2> {
  _GoodWidget2State();

  @override
  Widget build(BuildContext context) => const SizedBox();
}

Turning this rule off

This rule is in the recommended preset, so it is on with preset: recommended or preset: opinionated. Add it to preset: core with avoid_state_constructors: true.

To turn it off:

many_lints.yaml

rules:
  avoid_state_constructors: false

To keep the rule on but skip certain paths, use per-rule exclude.

Options

Projects with a state abstraction that does not extend Flutter’s State can opt that base class into this rule:

analysis_options.yaml

analysis_options.yaml

many_lints:
  rules:
    avoid_state_constructors:
      state_base_classes: [AppState]

many_lints.yaml

many_lints.yaml

rules:
  avoid_state_constructors:
    state_base_classes: [AppState]

Option	Type	Default	Description
state_base_classes	list of strings	[]	Additional non-State base classes whose subclasses should be treated as state classes

Related rules

• prefer_immutable_state — Ensure classes named as state are annotated with @immutable.
• avoid_empty_setstate — Don’t call setState with an empty callback.
• avoid_inherited_widget_in_initstate — Don’t look up inherited widgets inside initState.
• avoid_late_context — Don’t read BuildContext in a late field initializer.