dependencies:
  flutter:
    sdk: flutter
  reactive_forms

import 'package:reactive_forms/reactive_forms.dart';

class MyFormPage extends StatelessWidget {
  final form = FormGroup({
    'name': FormControl<String>(validators: [Validators.required]),
    'emails': FormArray<FormControl<String>>([]),
  });

  @override
  Widget build(BuildContext context) {
    return ReactiveForm(
      formGroup: form,
      child: Column(
        children: [
          ReactiveTextField(formControlName: 'name'),
          // Additional controls…
        ],
      ),
    );
  }
}

ReactiveForm(
  formGroup: form,
  child: Column(
    children: [
      ReactiveFormArray(
        formArrayName: 'emails',
        builder: (context, formArray, child) {
          return Column(
            children: [
              for (int i = 0; i < formArray.controls.length; i++)
                Row(
                  children: [
                    Expanded(
                      child: ReactiveTextField(
                        formControlName: i.toString(),
                        decoration: InputDecoration(labelText: 'Email #${i + 1}'),
                        validationMessages: {ValidationMessage.email: (_) => 'Invalid email'},
                      ),
                    ),
                    IconButton(
                      icon: Icon(Icons.remove_circle),
                      onPressed: () => formArray.removeAt(i),
                    ),
                  ],
                ),
              ElevatedButton(
                onPressed: () {
                  formArray.add(FormControl<String>(
                    validators: [Validators.required, Validators.email],
                  ));
                },
                child: Text('Add Email'),
              ),
            ],
          );
        },
      ),
    ],
  ),
)

Map<String, dynamic>? noBlacklist(AbstractControl control) {
  final value = control.value as String?;
  if (value != null && value.contains('badword')) {
    return {'blacklist': 'Contains forbidden term'};
  }
  return null;
}

final titleControl = FormControl<String>(
  validators: [Validators.required, noBlacklist],
);

Future<Map<String, dynamic>?> checkUsernameAsync(AbstractControl control) async {
  final username = control.value as String;
  final available = await apiService.isUsernameAvailable(username);
  return available ? null : {'usernameTaken': true};
}

final usernameControl = FormControl<String>(
  asyncValidators: [checkUsernameAsync],
);

void onSubmit() async {
  form.markAllAsTouched();
  if (form.invalid) return;

  try {
    final data = form.value;
    await apiService.submitProfile(data);
    // Handle success…
  } on ApiException catch (e) {
    form.setErrors({'submitError': e.message});
  }
}

// In the UI:
ReactiveFormConsumer(
  builder: (context, form, child) {
    final error = form.errors['submitError'];
    return error != null
      ? Text(error, style: TextStyle(color: Colors.red))
      : SizedBox.shrink();
  },
),