DART

flutter form validation

final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    // Build a Form widget using the _formKey created above.
    return Form(
      key: _formKey,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          TextFormField(
            // The validator receives the text that the user has entered.
            validator: (value) {
              if (value == null || value.isEmpty) {
                return 'Please enter some text';
              }
              return null;
            },
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: ElevatedButton(
              onPressed: () {
                // Validate returns true if the form is valid, or false otherwise.
                if (_formKey.currentState!.validate()) {
                  // If the form is valid, display a snackbar. In the real world,
                  // you'd often call a server or save the information in a database.
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('Processing Data')),
                  );
                }
              },
              child: const Text('Submit'),
            ),
          ),
        ],
      ),
    );

create and validate flutter forms

Build a form with validation - Flutter Cookbook
https://docs.flutter.dev/cookbook/forms/validation

validator in form field flutter

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mixin InputValidationMixin {
  bool isPasswordValid(String password) => password.length == 6;

  bool isEmailValid(String email) {
    Pattern pattern =
      r '^(([^<>()[].,;:s@"]+(.[^<>()[].,;:s@"]+)*)|(".+"))@(([[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}])|(([a-zA-Z-0-9]+.)+[a-zA-Z]{2,}))$';
    RegExp regex = new RegExp(pattern);
    return regex.hasMatch(email);
  }
}

create and validate flutter forms

Build a form with validation - Flutter Cookbook
https://docs.flutter.dev/cookbook/forms/validation

create and validate flutter forms

Build a form with validation - Flutter Cookbook
https://docs.flutter.dev/cookbook/forms/validation

create and validate flutter forms

Build a form with validation - Flutter Cookbook
https://docs.flutter.dev/cookbook/forms/validation