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

0 vote127 views1 answer
Path dart
Dart
3 votes104 views1 answer
Flutter how to space buttons evenly in a row
Dart
-1 vote118 views1 answer
Type '_InternalLinkedHashMap<DateTime, int>' is not a subtype of type 'Map<DateTime, double>'
Dart
26 votes234 views6 answers
Flutter snackbar
Dart
0 vote122 views2 answers
Search in array dart
Dart
7 votes104 views2 answers
Flutter build apk release target arm android
Dart
7 votes107 views2 answers
Flutter opacity
Dart
47 votes82 views10 answers
Flutter get width of screen
Dart
1 vote70 views2 answers
Error: unable to update dart sdk. retrying...
Dart
1 vote109 views2 answers
Flutter array filter
Dart