Reactive Forms

https://pub.dev/documentation/reactive_forms/latest
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Reactive Forms is a model-driven approach to handling form inputs and validations in Flutter,...
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### Install Reactive Forms dependency

Source: https://pub.dev/documentation/reactive_forms/latest/index.html

Add the package to your pubspec.yaml file to include it in your Flutter project.

```yaml
dependencies:
  flutter:
    sdk: flutter

  reactive_forms: ^18.2.2
```

--------------------------------

### Update FormGroup values example

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormGroup/updateValue.html

Demonstrates how to initialize a FormGroup and update its values using the updateValue method.

```dart
final form = FormGroup({
  'first': FormControl(),
  'last': FormControl(),
});

print(form.value); // outputs: { first: null, last: null }

form.updateValue({'first': 'John', 'last': 'Doe'});
print(form.value); // outputs: { first: 'John', last: 'Doe' }
```

--------------------------------

### Define a form component for testing

Source: https://pub.dev/documentation/reactive_forms/latest/index.html

Example of a StatefulWidget component structure, recommended to include Keys for widget testing.

```dart
class LoginForm extends StatefulWidget {
  const LoginForm({Key? key}) : super(key: key);

  @override
  LoginFormState createState() => LoginFormState();
}
```

--------------------------------

### Example Form Data Output

Source: https://pub.dev/documentation/reactive_forms/latest/index.html

The structure of the Map returned by accessing the form's value property.

```json
{
  "personal": {
    "name": "...",
    "email": "..."
  },
  "phone": {
    "phoneNumber": "...",
    "countryIso": "..."
  },
  "address": {
    "street": "...",
    "city": "...",
    "zip": "..."
  }
}
```

--------------------------------

### Define a FormGroup

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormGroup/control.html

Setup a FormGroup with nested controls to demonstrate path-based access.

```dart
final form = FormGroup({
  'total': FormControl<int>(value: 20),
  'person': FormGroup({
    'name': FormControl<String>(value: 'John'),
  }),
});
```

--------------------------------

### Create a FormControl with a default value

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormBuilder/control.html

Initializes a control with a specified starting value.

```dart
final name = fb.control('John Doe');
```

--------------------------------

### Get AbstractControl value

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/value.html

Retrieves the current value of the control.

```dart
T? get value => _value;
```

--------------------------------

### ReactiveSwitch.adaptive constructor

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveSwitch-class.html

Creates a ReactiveSwitch that adapts its appearance based on the target platform.

```APIDOC
## ReactiveSwitch.adaptive({Key? key, String? formControlName, FormControl<bool>? formControl, ...})

### Description
Creates a ReactiveSwitch that wraps a CupertinoSwitch if the target platform is iOS, or a material design switch otherwise.
```

--------------------------------

### Define ReactiveSliderLabelBuilder

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms

Signature for callbacks that are used to get the label of the ReactiveSlider.

```dart
ReactiveSliderLabelBuilder = String Function(double)
```

--------------------------------

### Implementation of subscribeControl

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFormFieldState/subscribeControl.html

Initializes subscriptions for control status and touch changes, and sets up the value accessor.

```dart
@protected
@mustCallSuper
void subscribeControl() {
  _statusChangesSubscription = control.statusChanged.listen(
    _onControlStatusChanged,
  );
  _touchChangesSubscription = control.touchChanges.listen(
    _onControlTouchChanged,
  );
  _subscribeValueAccessor();
}
```

--------------------------------

### FormArray reset example

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/reset.html

Resets a FormArray with a list of values for its descendants.

```dart
final array = FormArray<String>([
  FormControl<String>(),
  FormControl<String>(),
]);

array.reset(value: ['name', 'last name']);

print(array.value); // output: ['name', 'last name']
```

--------------------------------

### void focus()

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/focus.html

The focus method is an abstract method that provides a standard interface for setting focus on a control.

```APIDOC
## void focus()

### Description
Triggers focus on the control. This is an abstract method that must be implemented by concrete control classes.

### Signature
`void focus()`
```

--------------------------------

### Create FormGroup with FormBuilder

Source: https://pub.dev/documentation/reactive_forms/latest/index.html

Demonstrates the syntactic sugar provided by FormBuilder for group creation compared to standard FormGroup instantiation.

```dart
// Creates a group
final form = fb.group({
  'name': 'John Doe',
  'email': ['', Validators.required, Validators.email],
  'password': Validators.required,
});
```

```dart
final form = FormGroup({
  'name': FormControl<String>(value: 'John Doe'),
  'email': FormControl<String>(value: '', validators: [Validators.required, Validators.email]),
  'password': FormControl<String>(validators: [Validators.required]),
});
```

--------------------------------

### FormGroup reset example

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/reset.html

Resets a FormGroup with a map of values for its descendants.

```dart
final form = FormGroup({
  'first': FormControl(value: 'first name'),
  'last': FormControl(value: 'last name'),
});

print(form.value);   // output: {first: 'first name', last: 'last name'}

form.reset(value: { 'first': 'John', 'last': 'last name' });

print(form.value); // output: {first: 'John', last: 'last name'}
```

--------------------------------

### FormControl<T> get control

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveDatePickerDelegate/control.html

Retrieves the FormControl instance associated with the ReactiveTimePicker widget.

```APIDOC
## Property: control

### Description
Gets the FormControl bound to the ReactiveTimePicker widget.

### Signature
`FormControl<T> get control`
```

--------------------------------

### FocusNode get focusNode

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FocusController/focusNode.html

Retrieves the UI focus node registered with the controller.

```APIDOC
## FocusNode get focusNode

### Description
Gets the UI focus node registered with the controller. This allows developers to interact directly with the underlying Flutter FocusNode.

### Signature
`FocusNode get focusNode`

### Returns
- **FocusNode** - The focus node instance associated with the controller.
```

--------------------------------

### state<T>

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormBuilder-class.html

Creates a ControlState instance.

```APIDOC
### Method
state<T>({T? value, bool? disabled}) → ControlState<T>

### Description
Creates a ControlState object with an optional initial value and disabled status.
```

--------------------------------

### bool get hasFocus

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FocusController/hasFocus.html

Retrieves the current focus state of the focus controller.

```APIDOC
## bool get hasFocus

### Description
Returns the current focus state of the focus controller as a boolean value.

### Signature
`bool get hasFocus`

### Returns
- **bool** - True if the controller is currently focused, false otherwise.
```

--------------------------------

### FormControl reset example

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/reset.html

Resets a single FormControl with a specific initial value.

```dart
final control = FormControl<String>();

control.reset(value: 'John Doe');

print(control.value); // output: 'John Doe'
```

--------------------------------

### showPicker()

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveTimePickerDelegate-class.html

Displays the time picker dialog to the user.

```APIDOC
## showPicker()

### Description
Shows the time picker dialog.

### Signature
`void showPicker()`
```

--------------------------------

### void showPicker()

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveDatePickerDelegate/showPicker.html

Invokes the internal callback to display the time picker dialog associated with the field.

```APIDOC
## void showPicker()

### Description
Displays the time picker dialog for the associated reactive form field.

### Signature
`void showPicker()`
```

--------------------------------

### ReactiveSwitchListTile.adaptive

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveSwitchListTile/ReactiveSwitchListTile.adaptive.html

Creates a platform-adaptive switch list tile that is bound to a form control. It automatically adapts its appearance based on the platform (Material or Cupertino).

```APIDOC
## ReactiveSwitchListTile.adaptive

### Description
Creates a platform-adaptive switch list tile that integrates with a reactive form control. This widget automatically switches between Material and Cupertino styles based on the platform.

### Constructor Signature
ReactiveSwitchListTile.adaptive({
  Key? key,
  String? formControlName,
  FormControl<bool>? formControl,
  Color? activeColor,
  Color? activeTrackColor,
  Color? inactiveThumbColor,
  Color? inactiveTrackColor,
  ImageProvider? activeThumbImage,
  ImageErrorListener? onActiveThumbImageError,
  ImageProvider? inactiveThumbImage,
  ImageErrorListener? onInactiveThumbImageError,
  WidgetStateProperty<Color?>? thumbColor,
  WidgetStateProperty<Color?>? trackColor,
  WidgetStateProperty<Color?>? trackOutlineColor,
  WidgetStateProperty<Icon?>? thumbIcon,
  MaterialTapTargetSize? materialTapTargetSize,
  DragStartBehavior dragStartBehavior,
  MouseCursor? mouseCursor,
  WidgetStateProperty<Color?>? overlayColor,
  double? splashRadius,
  bool autofocus,
  bool? applyCupertinoTheme,
  EdgeInsetsGeometry? contentPadding,
  ListTileControlAffinity controlAffinity,
  bool? dense,
  bool? enableFeedback,
  FocusNode? focusNode,
  ValueChanged<bool>? onFocusChange,
  Color? hoverColor,
  bool isThreeLine,
  Widget? secondary,
  bool selected,
  Color? selectedTileColor,
  ShapeBorder? shape,
  Widget? subtitle,
  Color? tileColor,
  Widget? title,
  VisualDensity? visualDensity,
  ReactiveFormFieldCallback<bool>? onChanged
})
```

--------------------------------

### bool get touched

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFormFieldState/touched.html

Returns true if the widget has been touched, otherwise returns false.

```APIDOC
## bool get touched

### Description
Gets a boolean value indicating whether the form field has been touched. Returns true if the widget is touched, otherwise returns false.

### Signature
`bool get touched`
```

--------------------------------

### get value

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormGroup/value.html

Retrieves the current value of the FormGroup as a Map of control names to their respective values.

```APIDOC
## Map<String, Object?> get value

### Description
Returns the current value of the form group as an unmodifiable map containing the values of all child controls.

### Signature
`Map<String, Object?> get value`
```

--------------------------------

### Initialize FocusController

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FocusController/FocusController.html

Constructs a new FocusController instance. If no focusNode is provided, a new one is created and managed by the controller.

```dart
FocusController({FocusNode? focusNode})
  : _focusNode = focusNode ?? FocusNode(),
    _shouldDisposeFocusNode = focusNode == null {
  this.focusNode.addListener(_onFocusNodeFocusChanges);
}
```

--------------------------------

### Initialize FormBuilder instance

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/fb.html

Create a global instance of the FormBuilder class.

```dart
final fb = FormBuilder();
```

--------------------------------

### bool get isNotNull

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ControlExtension/isNotNull.html

Returns true if the value of the control is not null, otherwise returns false.

```APIDOC
## bool get isNotNull

### Description
Returns true if the value of the control is not null, otherwise returns false.

### Signature
`bool get isNotNull`
```

--------------------------------

### Widget build(BuildContext context)

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveStatusListenableBuilder/build.html

Describes the part of the user interface represented by this widget. The framework calls this method when the widget is inserted into the tree or when its dependencies change.

```APIDOC
## Widget build(BuildContext context)

### Description
Describes the part of the user interface represented by this widget. The framework calls this method when this widget is inserted into the tree in a given BuildContext and when the dependencies of this widget change.

### Parameters
- **context** (BuildContext) - The location in the tree at which this widget is being built.

### Implementation
```dart
@override
Widget build(BuildContext context) {
  var control = formControl;
  if (control == null) {
    final form = ReactiveForm.of(context, listen: false);
    if (form == null || form is! FormControlCollection) {
      throw FormControlParentNotFoundException(this);
    }

    final collection = form as FormControlCollection;
    control = collection.control(formControlName!);
  }

  return StreamBuilder<ControlStatus>(
    stream: control.statusChanged,
    builder: (context, snapshot) => builder(context, control!, child),
  );
}
```
```

--------------------------------

### bool get isNull

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ControlExtension/isNull.html

Returns true if the value of the control is null, otherwise returns false.

```APIDOC
## bool get isNull

### Description
Returns true if the value of the control is null, otherwise returns false.

### Signature
`bool get isNull`
```

--------------------------------

### void focus([String name = ''])

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormGroup/focus.html

Sets focus to a child control. The name argument is a dot-delimited string that defines the path to the control.

```APIDOC
## void focus([String name = ''])

### Description
Sets focus to a child control within the FormGroup. If a name is provided, it targets the control at the specified dot-delimited path. If no name is provided, it defaults to the first control in the collection.

### Parameters
- **name** (String) - Optional - A dot-delimited string representing the path to the child control.

### Usage Example
```dart
// Focus a child control by name
form.focus('name');

// Focus a nested child control by path
form.focus('person.name');
```
```

--------------------------------

### Example Error Map Structure

Source: https://pub.dev/documentation/reactive_forms/latest/index.html

The structure of the Map returned by FormControl.errors when a pattern validation fails.

```json
{
  "pattern": {
    "requiredPattern": "^3[47][0-9]{13}$",
    "actualValue": 395465465421
  }
}

```

--------------------------------

### bool get valid

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/valid.html

Returns true if the control's status is ControlStatus.valid, otherwise returns false.

```APIDOC
## bool get valid

### Description
Returns a boolean value indicating whether the control is currently in a valid state. A control is considered valid when its status is equal to ControlStatus.valid.

### Signature
`bool get valid`

### Returns
- **bool** - True if the control status is valid, false otherwise.
```

--------------------------------

### ReactiveSwitch.adaptive

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveSwitch/ReactiveSwitch.adaptive.html

Creates a platform-adaptive switch that binds to a reactive form control.

```APIDOC
## ReactiveSwitch.adaptive

### Description
Creates a ReactiveSwitch that wraps a CupertinoSwitch if the target platform is iOS, or a material design switch otherwise. It binds the switch state to a form control.

### Parameters
- **formControlName** (String) - Optional - The name of the FormControl to bind to.
- **formControl** (FormControl<bool>) - Optional - The FormControl instance to bind to.
- **activeColor** (Color) - Optional - The color to use when this switch is on.
- **activeTrackColor** (Color) - Optional - The color to use on the track when this switch is on.
- **inactiveThumbColor** (Color) - Optional - The color to use on the thumb when this switch is off.
- **inactiveTrackColor** (Color) - Optional - The color to use on the track when this switch is off.
- **onChanged** (ReactiveFormFieldCallback<bool>) - Optional - Called when the user toggles the switch.

### Usage
Must provide one of the arguments `formControl` or a `formControlName`, but not both at the same time.
```

--------------------------------

### Initialize a FormGroup

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormGroup/FormGroup.html

Create a new FormGroup instance by passing a map of child controls.

```dart
final form = FromGroup({
  'name': FormControl(defaultValue: 'John Doe'),
  'email': FormControl(),
});
```

--------------------------------

### bool get disabled

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/disabled.html

Returns true if the control's status is ControlStatus.disabled, otherwise returns false.

```APIDOC
## bool get disabled

### Description
A getter that returns a boolean value indicating if the control is currently disabled. A control is considered disabled when its status is set to `ControlStatus.disabled`.

### Signature
`bool get disabled`

### Returns
- **bool** - True if the control is disabled, false otherwise.
```

--------------------------------

### Implementation of control method

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormGroup/control.html

The internal logic for resolving control paths and handling missing controls.

```dart
@override
AbstractControl<dynamic> control(String name) {
  final namePath = name.split(_controlNameDelimiter);
  if (namePath.length > 1) {
    final control = findControlInCollection(namePath);
    if (control != null) {
      return control;
    }
  } else if (contains(name)) {
    return _controls[name]!;
  }

  throw FormControlNotFoundException(controlName: name);
}
```

--------------------------------

### Implementation of delegateAsync

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/Validators/delegateAsync.html

The internal implementation logic for the delegateAsync method, showing how it handles the debounceTime parameter.

```dart
static AsyncValidator<dynamic> delegateAsync(
  AsyncValidatorFunction validator, {
  int debounceTime = 0,
}) {
  final delegateValidator = DelegateAsyncValidator(validator);
  if (debounceTime > 0) {
    return DebouncedAsyncValidator(delegateValidator, debounceTime);
  }
  return delegateValidator;
}
```

--------------------------------

### FocusNode get focusNode

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFocusableFormFieldState/focusNode.html

Retrieves the FocusNode associated with the form field state, either from the internal _focusNode or the _focusController.

```APIDOC
## Property: focusNode

### Description
Returns the FocusNode object used by the stateful widget to obtain keyboard focus. This property is an override of the base class implementation.

### Signature
`FocusNode get focusNode`

### Implementation
```dart
@override
FocusNode get focusNode => _focusNode ?? _focusController.focusNode;
```
```

--------------------------------

### FormGroup addAll implementation

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormGroup/addAll.html

The internal implementation of the addAll method, showing how controls are added and state is updated.

```dart
void addAll(Map<String, AbstractControl<dynamic>> controls) {
  _controls.addAll(controls);
  controls.forEach((name, control) {
    control.parent = this;
  });
  updateValueAndValidity();
  updateTouched();
  updatePristine();
  emitsCollectionChanged(_controls.values.toList());
}
```

--------------------------------

### Using state<T> in a form group

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormBuilder/state.html

Demonstrates initializing a form group and resetting its state using the fb.state method.

```dart
final form = fb.group({
  'name': 'first name'
});

form.resetState({
  'name': fb.state(value: 'name'),
});

print(form.value); // output: {'name': 'name'}
```

--------------------------------

### Implement unmount in InheritedNotifierElement

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/InheritedNotifierElement/unmount.html

Example implementation of the unmount method, ensuring subscriptions are cancelled before calling the superclass method.

```dart
@override
void unmount() {
  _subscription.cancel();
  super.unmount();
}
```

--------------------------------

### FocusController Constructor

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FocusController-class.html

Constructs an instance of the FocusController, optionally accepting a FocusNode.

```APIDOC
### FocusController({FocusNode? focusNode})

Constructs an instance of the focus controller.
```

--------------------------------

### Implementation of markAsPristine

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/markAsPristine.html

The internal implementation of the markAsPristine method, showing how it updates the control's state and propagates the change to children and parents.

```dart
void markAsPristine({bool updateParent = true}) {
  _pristine = true;

  forEachChild((control) => control.markAsPristine(updateParent: false));

  if (updateParent) {
    parent?.updatePristine(updateParent: updateParent);
  }
}
```

--------------------------------

### FocusNode? get focusNode

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFormFieldState/focusNode.html

Retrieves the FocusNode associated with the reactive form field, allowing for programmatic control over keyboard focus.

```APIDOC
## Property: focusNode

### Description
Returns the `FocusNode` object used by the stateful widget to obtain or manage keyboard focus. This property is read-only and delegates to the underlying widget's focus node.

### Signature
`FocusNode? get focusNode`

### Returns
- **FocusNode?** - The focus node instance if available, otherwise null.
```

--------------------------------

### T? get defaultValue

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormControl/defaultValue.html

Retrieves the default value of the control. If nonNullable is true, it returns the initial value; if false, it returns null.

```APIDOC
## Property: defaultValue

### Description
Gets the default value of the control. This value is used when the reset method is called without providing a specific value.

### Signature
`T? get defaultValue`

### Behavior
- If `nonNullable` is `true` (default), this property holds the initial value provided to the constructor.
- If `nonNullable` is `false`, this property returns `null`.
```

--------------------------------

### of(BuildContext context)

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFormConfig-class.html

Static method to retrieve the nearest ReactiveFormConfig instance from the widget tree.

```APIDOC
## Static Method: of

### Description
Returns the nearest ReactiveFormConfig model up the widget tree.

### Parameters
- **context** (BuildContext) - Required - The build context to search from.

### Returns
- **ReactiveFormConfig?** - The nearest ReactiveFormConfig instance found, or null if none exists.
```

--------------------------------

### showPicker()

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveDatePickerDelegate-class.html

Triggers the display of the date picker dialog.

```APIDOC
### Method
void showPicker()

### Description
Shows the date picker dialog associated with the delegate instance.
```

--------------------------------

### bool get isNullOrEmpty

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/StringControlExtension/isNullOrEmpty.html

Returns true if the value of the control is null or an empty white spaces string, otherwise returns false.

```APIDOC
## isNullOrEmpty

### Description
Returns true if the value of the control is null or an empty white spaces string, otherwise returns false.

### Signature
`bool get isNullOrEmpty`
```

--------------------------------

### ReactiveFormConfig(child, validationMessages, key)

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFormConfig/ReactiveFormConfig.html

Creates an instance of ReactiveFormConfig to define global configurations at the application level.

```APIDOC
## ReactiveFormConfig Constructor

### Description
Creates an instance of ReactiveFormConfig. This widget is used to define global configurations, specifically validation messages, at the application level.

### Signature
`const ReactiveFormConfig({required Widget child, required Map<String, ValidationMessageFunction> validationMessages, Key? key})`

### Parameters
- **child** (Widget) - Required - The child widget to be wrapped by the configuration.
- **validationMessages** (Map<String, ValidationMessageFunction>) - Required - A map defining global validation messages for specific validation keys.
- **key** (Key) - Optional - The widget key.

### Example
```dart
ReactiveFormConfig(
  validationMessages: {
    ValidationMessage.required: (_) => 'Field must not be empty',
  },
  child: MaterialApp(...)
);
```
```

--------------------------------

### get controls

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormGroup/controls.html

Retrieves the collection of child controls associated with the FormGroup. The keys in the map represent the names under which each child control is registered.

```APIDOC
## Property: controls

### Description
Gets the collection of child controls registered within the FormGroup. The returned map is unmodifiable.

### Signature
`Map<String, AbstractControl<Object?>> get controls`

### Returns
- **Map<String, AbstractControl<Object?>>** - A map where keys are control names and values are the corresponding AbstractControl instances.
```

--------------------------------

### bool get dirty

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/dirty.html

Returns true if the user has changed the value of the control in the UI. Programmatic changes do not mark the control as dirty.

```APIDOC
## Property: dirty

### Description
Returns a boolean indicating if the control has been modified by the user in the UI. Programmatic changes to the control's value do not mark it as dirty.

### Signature
`bool get dirty`

### Returns
- **bool**: True if the control is dirty, false otherwise.
```

--------------------------------

### ReactiveSwitchListTile.adaptive

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveSwitchListTile/ReactiveSwitchListTile.adaptive.html

Creates a ReactiveSwitchListTile that wraps a Material ListTile with an adaptive Switch, following Material design's cross-platform guidelines.

```APIDOC
## ReactiveSwitchListTile.adaptive

### Description
Creates a ReactiveSwitchListTile that wraps a Material ListTile with an adaptive Switch. It uses Switch.adaptive to change the graphics based on the ambient ThemeData.platform, using CupertinoSwitch on iOS/macOS and Material Switch on other platforms.

### Constructor Signature
ReactiveSwitchListTile.adaptive({
  Key? key,
  String? formControlName,
  FormControl<bool>? formControl,
  Color? activeColor,
  Color? activeTrackColor,
  Color? inactiveThumbColor,
  Color? inactiveTrackColor,
  ImageProvider<Object>? activeThumbImage,
  ImageErrorListener? onActiveThumbImageError,
  ImageProvider<Object>? inactiveThumbImage,
  ImageErrorListener? onInactiveThumbImageError,
  WidgetStateProperty<Color?>? thumbColor,
  WidgetStateProperty<Color?>? trackColor,
  WidgetStateProperty<Color?>? trackOutlineColor,
  WidgetStateProperty<Icon?>? thumbIcon,
  MaterialTapTargetSize? materialTapTargetSize,
  DragStartBehavior dragStartBehavior = DragStartBehavior.start,
  MouseCursor? mouseCursor,
  WidgetStateProperty<Color?>? overlayColor,
  double? splashRadius,
  bool autofocus = false,
  bool? applyCupertinoTheme,
  EdgeInsetsGeometry? contentPadding,
  ListTileControlAffinity controlAffinity = ListTileControlAffinity.platform,
  bool? dense,
  bool? enableFeedback,
  FocusNode? focusNode,
  ValueChanged<bool>? onFocusChange,
  Color? hoverColor,
  bool isThreeLine = false,
  Widget? secondary,
  bool selected = false,
  Color? selectedTileColor,
  ShapeBorder? shape,
  Widget? subtitle,
  Color? tileColor,
  Widget? title,
  VisualDensity? visualDensity,
  ReactiveFormFieldCallback<bool>? onChanged
})
```

--------------------------------

### Invalid StatefulWidget build pattern

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFocusableFormFieldState/build.html

An example of an invalid pattern where a build method on a StatefulWidget could lead to stale closure captures.

```dart
// (this is not valid Flutter code)
class MyButton extends StatefulWidgetX {
  MyButton({super.key, required this.color});

  final Color color;

  @override
  Widget build(BuildContext context, State state) {
    return SpecialWidget(
      handler: () { print('color: $color'); },
    );
  }
}
```

--------------------------------

### Implement Focus Flow Between Fields

Source: https://pub.dev/documentation/reactive_forms/latest/index.html

Configure form fields to transition focus using textInputAction and onSubmitted callbacks.

```dart
final form = fb.group({
  'name': ['', Validators.required],
  'email': ['', Validators.required, Validators.email],
  'password': ['', Validators.required],
});
```

```dart
@override
Widget build(BuildContext context) {
  return ReactiveForm(
    formGroup: this.form,
    child: Column(
      children: <Widget>[
        ReactiveTextField(
          formControlName: 'name',
          textInputAction: TextInputAction.next,
          onSubmitted: () => this.form.focus('email'),
        ),
        ReactiveTextField(
          formControlName: 'email',
          textInputAction: TextInputAction.next,
          onSubmitted: () => this.form.focus('password'),
        ),
        ReactiveTextField(
          formControlName: 'password',
          obscureText: true,
        ),
      ],
    ),
  );
}
```

--------------------------------

### void markAsPristine({bool updateParent = true})

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/markAsPristine.html

Marks the control as pristine. If the control has children, it recursively marks all children as pristine and optionally updates the pristine status of parent controls.

```APIDOC
## markAsPristine

### Description
Marks the control as pristine. If the control has any children, it marks all children as pristine and recalculates the pristine status of all parent controls.

### Signature
`void markAsPristine({bool updateParent = true})`

### Parameters
- **updateParent** (bool) - Optional - When true (default), marks all direct ancestors as pristine. When false, marks only the current control.
```

--------------------------------

### T get rawValue

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormControlCollection/rawValue.html

Retrieves the value of the control, including any disabled controls. This method returns all values regardless of the disabled status of child controls.

```APIDOC
## Property: rawValue

### Description
Gets the value of the control, including any disabled control. Retrieves all values regardless of disabled status of children controls.

### Signature
`T get rawValue;`
```

--------------------------------

### ControlStatus get status

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/status.html

Retrieves the current validation status of the control. The status indicates whether the control has passed validation, failed, is currently validating, or is disabled.

```APIDOC
## status

### Description
Returns the validation status of the control. The status values are mutually exclusive.

### Signature
`ControlStatus get status`

### Possible Values
- **VALID**: The control has passed all validation checks.
- **INVALID**: The control has failed at least one validation check.
- **PENDING**: The control is currently performing a validation check.
- **DISABLED**: The control is exempt from ancestor calculations of validity or value.
```

--------------------------------

### Initialize FormBuilderInvalidInitializationException

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormBuilderInvalidInitializationException/FormBuilderInvalidInitializationException.html

Instantiate the exception by providing a custom error message.

```dart
FormBuilderInvalidInitializationException(this.message);
```

--------------------------------

### Initialize FormGroup

Source: https://pub.dev/documentation/reactive_forms/latest/index.html

Defines a FormGroup with initial values for name and email controls.

```dart
final form = FormGroup({
  'name': FormControl<String>(value: 'John Doe'),
  'email': FormControl<String>(value: 'johndoe@email.com'),
});
```

--------------------------------

### bool get touched

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/touched.html

Returns a boolean value indicating if the control is touched. A control is marked as touched when the user interacts with the ReactiveFormField widget and subsequently removes focus or completes text entry.

```APIDOC
## bool get touched

### Description
Gets whether the control is touched or not. A control is considered touched when the user taps on the ReactiveFormField widget and then removes focus or completes the text edition. Validation messages typically begin to show up when the FormControl is touched.

### Return Value
- **bool** - True if the control has been touched, false otherwise.
```

--------------------------------

### void unmount()

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/InheritedNotifierElement/unmount.html

Transitions the element to the defunct state and releases held resources. Implementations must call super.unmount().

```APIDOC
## void unmount()

### Description
Transitions the element from the 'inactive' to the 'defunct' lifecycle state. This method is called when the framework determines an element will not be reactivated, and it is responsible for releasing resources held by the element.

### Usage
Implementations of this method should perform necessary cleanup and end with a call to `super.unmount()`.

### Implementation Example
```dart
@override
void unmount() {
  _subscription.cancel();
  super.unmount();
}
```
```

--------------------------------

### Initialize ControlState

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ControlState/ControlState.html

Constructs a new instance with optional value and disabled parameters.

```dart
ControlState({this.value, this.disabled});
```

--------------------------------

### AbstractControl<T> constructor

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/AbstractControl/AbstractControl.html

Initializes a new instance of AbstractControl with specified validation rules and initial state.

```APIDOC
## AbstractControl<T> constructor

### Description
Initializes a new AbstractControl instance. This constructor sets up the initial validation logic, asynchronous validation configuration, and the starting state (disabled/touched) of the control.

### Parameters
- **validators** (List<Validator>) - Optional - A list of synchronous validators to apply to the control.
- **asyncValidators** (List<AsyncValidator>) - Optional - A list of asynchronous validators to apply to the control.
- **asyncValidatorsDebounceTime** (int) - Optional - DEPRECATED: The debounce time in milliseconds for asynchronous validators. Defaults to 250.
- **disabled** (bool) - Optional - Whether the control should be initialized in a disabled state. Defaults to false.
- **touched** (bool) - Optional - Whether the control should be initialized in a touched state. Defaults to false.
```

--------------------------------

### ReactiveDatePicker Constructor

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveDatePicker-class.html

Creates a ReactiveDatePicker widget that wraps the showDatePicker function. It requires a builder to define the UI and specific date constraints.

```APIDOC
## ReactiveDatePicker(constructor)

### Description
Creates a ReactiveDatePicker that wraps the function showDatePicker. The formControlName is required to bind this ReactiveDatePicker to a FormControl.

### Parameters
- **formControlName** (String) - Optional - The name of the FormControl that is bound to this widget.
- **formControl** (FormControl<T>) - Optional - The control that is bound to this widget.
- **builder** (ReactiveDatePickerBuilder<T>) - Required - A builder function to define the UI that triggers the picker.
- **firstDate** (DateTime) - Required - The earliest allowable date.
- **lastDate** (DateTime) - Required - The latest allowable date.
- **initialEntryMode** (DatePickerEntryMode) - Optional - The initial entry mode for the date picker (defaults to DatePickerEntryMode.calendar).

### Example
```dart
ReactiveDatePicker(
  formControlName: 'birthday',
  builder: (context, picker, child) {
    return IconButton(
      onPressed: picker.showPicker,
      icon: Icon(Icons.date_range),
    );
  },
)
```
```

--------------------------------

### Initialize ReactiveFormConfig

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFormConfig/ReactiveFormConfig.html

Use this to define global validation messages at the application level.

```dart
ReactiveFormConfig(
  validationMessages: {
    ValidationMessage.required: (_) => 'Field must not be empty',
  },
  child: MaterialApp(...)
);
```

--------------------------------

### ReactiveFocusableFormFieldState<T, V>()

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFocusableFormFieldState/ReactiveFocusableFormFieldState.html

The constructor for initializing a new instance of ReactiveFocusableFormFieldState.

```APIDOC
## ReactiveFocusableFormFieldState<T, V>()

### Description
Creates a new instance of the ReactiveFocusableFormFieldState class.

### Signature
ReactiveFocusableFormFieldState<T, V>()
```

--------------------------------

### fb

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/fb.html

The global FormBuilder instance used to initialize form structures.

```APIDOC
## fb

### Description
A global instance of the FormBuilder class used to simplify the creation of form controls, groups, and arrays.

### Usage
```dart
final fb = FormBuilder();
```
```

--------------------------------

### ReactiveFormConsumer Constructor Implementation

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFormConsumer/ReactiveFormConsumer.html

The standard constructor for creating a ReactiveFormConsumer instance.

```dart
const ReactiveFormConsumer({super.key, required this.builder, this.child});
```

--------------------------------

### ReactiveSwitch(constructor)

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveSwitch/ReactiveSwitch.html

Creates a ReactiveSwitch that wraps a material design switch. You must provide either a formControl or a formControlName, but not both.

```APIDOC
## ReactiveSwitch(constructor)

### Description
Creates a ReactiveSwitch that wraps a material design switch. It binds to a FormControl to manage the switch state.

### Parameters
- **key** (Key?) - Optional - The widget key.
- **formControlName** (String?) - Optional - The name of the form control to bind to.
- **formControl** (FormControl<bool>?) - Optional - The form control instance to bind to.
- **focusNode** (FocusNode?) - Optional - The focus node for the switch.
- **activeColor** (Color?) - Optional - The color to use when the switch is on.
- **activeTrackColor** (Color?) - Optional - The color to use for the track when the switch is on.
- **inactiveThumbColor** (Color?) - Optional - The color to use for the thumb when the switch is off.
- **inactiveTrackColor** (Color?) - Optional - The color to use for the track when the switch is off.
- **activeThumbImage** (ImageProvider<Object>?) - Optional - An image to use on the thumb when the switch is on.
- **onActiveThumbImageError** (ImageErrorListener?) - Optional - Callback for errors loading the active thumb image.
- **inactiveThumbImage** (ImageProvider<Object>?) - Optional - An image to use on the thumb when the switch is off.
- **onInactiveThumbImageError** (ImageErrorListener?) - Optional - Callback for errors loading the inactive thumb image.
- **materialTapTargetSize** (MaterialTapTargetSize?) - Optional - Configures the tap target size.
- **dragStartBehavior** (DragStartBehavior) - Optional - Determines the behavior of drag start events.
- **focusColor** (Color?) - Optional - The color for the focus state.
- **hoverColor** (Color?) - Optional - The color for the hover state.
- **autofocus** (bool) - Optional - Whether the switch should autofocus.
- **padding** (EdgeInsetsGeometry?) - Optional - Padding around the switch.
- **trackOutlineWidth** (WidgetStateProperty<double?>?) - Optional - The width of the track outline.
- **thumbColor** (WidgetStateProperty<Color?>?) - Optional - The color of the thumb.
- **trackColor** (WidgetStateProperty<Color?>?) - Optional - The color of the track.
- **mouseCursor** (MouseCursor?) - Optional - The mouse cursor to show when hovering.
- **overlayColor** (WidgetStateProperty<Color?>?) - Optional - The color of the overlay.
- **splashRadius** (double?) - Optional - The radius of the splash effect.
- **onChanged** (ReactiveFormFieldCallback<bool>?) - Optional - Callback triggered when the value changes.
- **trackOutlineColor** (WidgetStateProperty<Color?>?) - Optional - The color of the track outline.
- **thumbIcon** (WidgetStateProperty<Icon?>?) - Optional - The icon to display on the thumb.
- **onFocusChange** (ValueChanged<bool>?) - Optional - Callback triggered when focus changes.
```

--------------------------------

### Implementation of showPicker

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveDatePickerDelegate/showPicker.html

This method invokes the internal callback associated with the field to display the picker.

```dart
void showPicker() {
  _showPickerCallback(_field);
}
```

--------------------------------

### ReactiveStatusListenableBuilder(Key? key, String? formControlName, AbstractControl<Object?>? formControl, required ReactiveListenableWidgetBuilder<Object?> builder, Widget? child)

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveStatusListenableBuilder/ReactiveStatusListenableBuilder.html

Creates an instance of ReactiveStatusListenableBuilder. You must provide either a formControlName or a formControl, but not both.

```APIDOC
## ReactiveStatusListenableBuilder

### Description
Creates an instance of ReactiveStatusListenableBuilder to listen to form control status changes.

### Parameters
- **key** (Key?) - Optional - The widget key.
- **formControlName** (String?) - Optional - The name of the form control to listen to.
- **formControl** (AbstractControl<Object?>?) - Optional - The form control instance to listen to.
- **builder** (ReactiveListenableWidgetBuilder<Object?>) - Required - The builder function that returns the widget.
- **child** (Widget?) - Optional - A child widget to be passed to the builder.
```

--------------------------------

### ReactiveSwitchListTile.adaptive Constructor Definition

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveSwitchListTile/ReactiveSwitchListTile.adaptive.html

The constructor signature and implementation for ReactiveSwitchListTile.adaptive, mapping form control state to the underlying SwitchListTile.adaptive widget.

```dart
ReactiveSwitchListTile.adaptive({
  super.key,
  super.formControlName,
  super.formControl,
  Color? activeColor,
  Color? activeTrackColor,
  Color? inactiveThumbColor,
  Color? inactiveTrackColor,
  ImageProvider? activeThumbImage,
  ImageErrorListener? onActiveThumbImageError,
  ImageProvider? inactiveThumbImage,
  ImageErrorListener? onInactiveThumbImageError,
  WidgetStateProperty<Color?>? thumbColor,
  WidgetStateProperty<Color?>? trackColor,
  WidgetStateProperty<Color?>? trackOutlineColor,
  WidgetStateProperty<Icon?>? thumbIcon,
  MaterialTapTargetSize? materialTapTargetSize,
  DragStartBehavior dragStartBehavior = DragStartBehavior.start,
  MouseCursor? mouseCursor,
  WidgetStateProperty<Color?>? overlayColor,
  double? splashRadius,
  bool autofocus = false,
  bool? applyCupertinoTheme,
  EdgeInsetsGeometry? contentPadding,
  ListTileControlAffinity controlAffinity = ListTileControlAffinity.platform,
  bool? dense,
  bool? enableFeedback,
  super.focusNode,
  ValueChanged<bool>? onFocusChange,
  Color? hoverColor,
  bool isThreeLine = false,
  Widget? secondary,
  bool selected = false,
  Color? selectedTileColor,
  ShapeBorder? shape,
  Widget? subtitle,
  Color? tileColor,
  Widget? title,
  VisualDensity? visualDensity,
  ReactiveFormFieldCallback<bool>? onChanged,
}) : super(
       builder: (field) {
         return SwitchListTile.adaptive(
           value: field.value ?? false,
           activeColor: activeColor,
           activeTrackColor: activeTrackColor,
           inactiveThumbColor: inactiveThumbColor,
           inactiveTrackColor: inactiveTrackColor,
           activeThumbImage: activeThumbImage,
           onActiveThumbImageError: onActiveThumbImageError,
           inactiveThumbImage: inactiveThumbImage,
           onInactiveThumbImageError: onInactiveThumbImageError,
           thumbColor: thumbColor,
           trackColor: trackColor,
           trackOutlineColor: trackOutlineColor,
           thumbIcon: thumbIcon,
           materialTapTargetSize: materialTapTargetSize,
           dragStartBehavior: dragStartBehavior,
           mouseCursor: mouseCursor,
           overlayColor: overlayColor,
           splashRadius: splashRadius,
           autofocus: autofocus,
           applyCupertinoTheme: applyCupertinoTheme,
           contentPadding: contentPadding,
           controlAffinity: controlAffinity,
           dense: dense,
           enableFeedback: enableFeedback,
           focusNode: field.focusNode,
           onFocusChange: onFocusChange,
           hoverColor: hoverColor,
           isThreeLine: isThreeLine,
           secondary: secondary,
           selected: selected,
           selectedTileColor: selectedTileColor,
           shape: shape,
           subtitle: subtitle,
           tileColor: tileColor,
           title: title,
           visualDensity: visualDensity,
           onChanged:
               field.control.enabled
                   ? (value) {
                     field.didChange(value);
                     onChanged?.call(field.control);
                   }
                   : null,
         );
       },
     );
```

--------------------------------

### ReactiveForm.of(BuildContext context, {bool listen = true})

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveForm/of.html

Retrieves the nearest AbstractControl from the widget tree. If listen is true, the widget will rebuild when the control changes.

```APIDOC
## ReactiveForm.of

### Description
Returns the nearest AbstractControl up the widget tree. If `listen` is set to `true` (default), the widget will rebuild whenever the model changes. Set `listen` to `false` to avoid unnecessary rebuilds.

### Signature
`static AbstractControl<Object>? of(BuildContext context, {bool listen = true})`

### Parameters
- **context** (BuildContext) - Required - The build context used to look up the inherited widget.
- **listen** (bool) - Optional - Whether to register the widget as a dependent that rebuilds on changes. Defaults to `true`.

### Returns
- **AbstractControl<Object>?** - The nearest form control found in the tree, or null if none exists.
```

--------------------------------

### ReactiveFormBuilder<T> constructor

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveFormBuilder/ReactiveFormBuilder.html

Creates an instance of ReactiveFormBuilder. The form and builder arguments are required.

```APIDOC
## ReactiveFormBuilder<T> constructor

### Description
Creates an instance of ReactiveFormBuilder. The `form` and `builder` arguments must not be null.

### Parameters
- **key** (Key?) - Optional - The widget key.
- **form** (ReactiveFormBuilderCreator) - Required - A function that creates the form group.
- **builder** (ReactiveFormConsumerBuilder) - Required - A builder function that provides the context, form group, and child widget.
- **canPop** (ReactiveFormCanPopCallback?) - Optional - A callback to determine if the route can be popped based on the form state.
- **onPopInvokedWithResult** (ReactiveFormPopInvokedWithResultCallback<T>?) - Optional - A callback invoked when the route is popped.
- **child** (Widget?) - Optional - A child widget to be passed to the builder.
```

--------------------------------

### ReactiveSwitch.adaptive Implementation

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/ReactiveSwitch/ReactiveSwitch.adaptive.html

The constructor implementation that maps reactive form field state to a platform-adaptive Switch widget.

```dart
ReactiveSwitch.adaptive({
  super.key,
  super.formControlName,
  super.formControl,
  super.focusNode,
  Color? activeColor,
  Color? activeTrackColor,
  Color? inactiveThumbColor,
  Color? inactiveTrackColor,
  ImageProvider? activeThumbImage,
  ImageErrorListener? onActiveThumbImageError,
  ImageProvider? inactiveThumbImage,
  ImageErrorListener? onInactiveThumbImageError,
  MaterialTapTargetSize? materialTapTargetSize,
  DragStartBehavior dragStartBehavior = DragStartBehavior.start,
  Color? focusColor,
  Color? hoverColor,
  bool autofocus = false,
  ValueChanged<bool>? onFocusChange,
  EdgeInsetsGeometry? padding,
  bool? applyCupertinoTheme,
  WidgetStateProperty<Color?>? thumbColor,
  WidgetStateProperty<Icon?>? thumbIcon,
  WidgetStateProperty<Color?>? trackColor,
  WidgetStateProperty<double?>? trackOutlineWidth,
  WidgetStateProperty<Color?>? trackOutlineColor,
  WidgetStateProperty<Color?>? overlayColor,
  MouseCursor? mouseCursor,
  double? splashRadius,
  ReactiveFormFieldCallback<bool>? onChanged,
}) : super(
       builder: (field) {
         return Switch.adaptive(
           value: field.value ?? false,
           activeColor: activeColor,
           activeTrackColor: activeTrackColor,
           inactiveThumbColor: inactiveThumbColor,
           inactiveTrackColor: inactiveTrackColor,
           activeThumbImage: activeThumbImage,
           onActiveThumbImageError: onActiveThumbImageError,
           inactiveThumbImage: inactiveThumbImage,
           onInactiveThumbImageError: onInactiveThumbImageError,
           materialTapTargetSize: materialTapTargetSize,
           dragStartBehavior: dragStartBehavior,
           focusColor: focusColor,
           hoverColor: hoverColor,
           thumbColor: thumbColor,
           thumbIcon: thumbIcon,
           trackColor: trackColor,
           trackOutlineWidth: trackOutlineWidth,
           trackOutlineColor: trackOutlineColor,
           mouseCursor: mouseCursor,
           overlayColor: overlayColor,
           splashRadius: splashRadius,
           autofocus: autofocus,
           padding: padding,
           applyCupertinoTheme: applyCupertinoTheme,
           onFocusChange: onFocusChange,
           focusNode: field.focusNode,
           onChanged:
               field.control.enabled
                   ? (value) {
                     field.didChange(value);
                     onChanged?.call(field.control);
                   }
                   : null,
         );
       },
     );
```

--------------------------------

### Implement ReactiveForm with external state management

Source: https://pub.dev/documentation/reactive_forms/latest/index.html

Demonstrates using ReactiveForm within a StatelessWidget by resolving the FormGroup from a provider.

```dart
// Using ReactiveForm in a StatelessWidget and resolving the FormGroup from a provider
class SignInForm extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final viewModel = Provider.of<SignInViewModel>(context, listen: false);

    return ReactiveForm(
      formGroup: viewModel.form,
      child: ReactiveTextField(
        formControlName: 'email',
      ),
    );
  }
}
```

--------------------------------

### FormBuilderInvalidInitializationException constructor

Source: https://pub.dev/documentation/reactive_forms/latest/reactive_forms/FormBuilderInvalidInitializationException/FormBuilderInvalidInitializationException.html

Creates an instance of the FormBuilderInvalidInitializationException with a provided error message.

```APIDOC
## FormBuilderInvalidInitializationException(String message)

### Description
Creates an instance of the exception with the specified message.

### Parameters
- **message** (String) - Required - The error message describing the invalid initialization.
```
Tokens:
Raw