required static method

String? required(
  1. dynamic value, {
  2. String? fieldName,
})

Validates that a field is not empty if required.

Returns error message if validation fails, null otherwise.

Implementation

static String? required(dynamic value, {String? fieldName}) {
  if (value == null) {
    return '${fieldName ?? "This field"} is required.';
  }

  if (value is String && value.trim().isEmpty) {
    return '${fieldName ?? "This field"} is required.';
  }

  if (value is List && value.isEmpty) {
    return '${fieldName ?? "This field"} is required.';
  }

  if (value is Map && value.isEmpty) {
    return '${fieldName ?? "This field"} is required.';
  }

  return null;
}