required<T> static method

Validator<T> required<T>(
  1. String message
)

Required field validator.

Implementation

static Validator<T> required<T>(String message) {
  return (value) {
    if (value == null) {
      return ValidationResult.invalid(message);
    }
    if (value is String && value.trim().isEmpty) {
      return ValidationResult.invalid(message);
    }
    if (value is Iterable && value.isEmpty) {
      return ValidationResult.invalid(message);
    }
    return const ValidationResult.valid();
  };
}