validateName function

String? validateName(
  1. String? name, {
  2. String fieldName = 'Name',
  3. int minLen = 1,
  4. int maxLength = 40,
})

Implementation

String? validateName(String? name,
    {String fieldName = 'Name', int minLen = 1, int maxLength = 40}) {
  if (name == null || name.isEmpty) {
    return 'Please Enter $fieldName';
  } else if (name.length < minLen) {
    return fieldName + ' must be $minLen characters long';
  } else if (name.length > maxLength) {
    return fieldName + ' must be less than $maxLength characters';
  } else {
    final regx = RegExp(r'^[a-z]+$').hasMatch(name);
    if (regx) {
      return null;
    } else {
      return fieldName + ' must contain letters only';
    }
  }
}