Result Type for Dart

Content

• Features
• Requirements
• Install
• Example
• Support
• License

Features

Result is a type that represents either Success or Failure.

Inspired by functional programming, Rust and Swift.

Requirements

• Dart: 2.12.0+

Install

dependencies:
  result_type: ^0.1.0

Example

The detailed example can be found at result_type/example/example.dart.

import 'dart:async';
import 'dart:convert';
import 'dart:math';

import 'package:http/http.dart' as http;
import 'package:result_type/result_type.dart';

void main() async {
  final random = Random();
  final client = http.Client();
  final result = await getPhotos(client);

  /// Do something with successful operation results or handle an error.
  if (result.isSuccess) {
    print('Photos Items: ${result.success}');
  } else {
    print('Error: ${result.failure}');
  }

  /// Apply transformation to successful operation results or handle an error.
  if (result.isSuccess) {
    final items = result.map((i) => i.where((j) => j.title.length > 60)).success;
    print('Number of Long Titles: ${items.length}');
  } else {
    print('Error: ${result.failure}');
  }

  /// In this example, note the difference in the result of using `map` and
  /// `flatMap` with a transformation that returns an result type.
  Result<int, Error> getNextInteger() => Success(random.nextInt(4));
  Result<int, Error> getNextAfterInteger(int n) => Success(random.nextInt(n + 1));

  final nextIntegerNestedResults = getNextInteger().map(getNextAfterInteger);
  print(nextIntegerNestedResults.runtimeType);
  /// `Prints`: Success<Result<int, Error>, dynamic>

  final nextIntegerUnboxedResults =  getNextInteger().flatMap(getNextAfterInteger);
  print(nextIntegerUnboxedResults.runtimeType);
  /// `Prints`: Success<int, Error>

  /// Use completion handler / callback style API if you want to.
  await getPhotos(client)
    ..result((photos) {
      print('Photos: $photos');
    }, (error) {
      print('Error: $error');
    });
}

To see examples of the following package in action:

cd example && dart run

Support

Post issues and feature requests on the GitHub issue tracker.

License

The source code of Result Type project is available under the Apache license. See the LICENSE file for more info.