devhammed / result_in_dart

Dart implementation of Rust's `[Result]` type.

result_in_dart

Dart implementation of Rust's [Result] type.

Result<T, E> is the type used for returning and propagating errors. It is a class with the two variants, [Ok(T)] and [Err(E)]. where [T] is the type of a successful value and [E] is the type of an error.

Loosely based on https://doc.rust-lang.org/src/core/result.rs.html source code.

import 'package:result_in_dart/result_in_dart.dart';

enum Version {
  version1,
  version2;
}

Result<Version, String> parseVersion(int versionNum) {
  if (versionNum == 1) {
    return const Ok(Version.version1);
  }

  if (versionNum == 2) {
    return const Ok(Version.version2);
  }

  return const Err('invalid version');
}

void main() {
  final version = parseVersion(1);

  // you can then unwrap...
  if (version.isOk()) {
    print('unwrap: working with version: ${version.unwrap()}');
  } else {
    print('unwrap: error parsing header: ${version.unwrapErr()}');
  }

  // or mapping...
  parseVersion(1).mapOrElse(
    (err) => print('mapOrElse: error parsing header: $err'),
    (v) => print('mapOrElse: working with version: $v'),
  );

  // or using Dart 3.0 patterns...
  if (version case Ok(value: Version v)) {
    print('patterns: working with version: $v');
  }

  if (version case Err(value: String err)) {
    print('patterns: error parsing header: $err');
  }

  // unwrapping using the ~ operator
  final a = Ok(1);
  final b = Ok(2);

  print('~ operator: ${~a + ~b}');
}