Create a validator in flutter

TextFormField(
  // The validator receives the text that the user has entered.
  validator: (value) {
    if (value.isEmpty) {
      return 'Please enter some text';
    }
    return null;
  },
);

Source: flutter.dev

Similar codes

4 votes187 views1 answer
How to Create Number Inputfield in Flutter?
Dart
13 votes181 views2 answers
Flutter column text direction
Dart
0 vote212 views1 answer
Dart The instance member 'user' can't be accessed in an initializer.Try replacing the reference to the instance member with a different expression
Dart
0 vote211 views1 answer
Dart convert int string leading zeros
Dart
0 vote192 views2 answers
Flutter how to disable splash on listview
Dart
12 votes167 views4 answers
Flutter substring
Dart
0 vote179 views1 answer
Next row column in flutter
Dart
13 votes198 views3 answers
Flutter get
Dart
0 vote184 views1 answer
Flutter default device font PlatformChannel
Dart
5 votes170 views1 answer
Dartpad missing browser localstorage
Dart