pattern static method

FormFieldValidator<String> pattern(
  1. RegExp regex, [
  2. String message = 'Invalid format'
])

Fails when a non-empty value doesn't match regex.

Implementation

static FormFieldValidator<String> pattern(
  RegExp regex, [
  String message = 'Invalid format',
]) =>
    (value) => (value == null || value.isEmpty || regex.hasMatch(value))
        ? null
        : message;