https://github.com/minikin/result_type
💊 Result Type for Dart represents either a success or a failure, including an associated value in each case.
https://github.com/minikin/result_type
dart either flutter functional-programming result result-type
Last synced: 7 months ago
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💊 Result Type for Dart represents either a success or a failure, including an associated value in each case.
- Host: GitHub
- URL: https://github.com/minikin/result_type
- Owner: minikin
- License: mit
- Created: 2022-06-14T11:27:35.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2024-04-30T09:49:56.000Z (over 1 year ago)
- Last Synced: 2025-03-08T17:54:25.733Z (7 months ago)
- Topics: dart, either, flutter, functional-programming, result, result-type
- Language: Dart
- Homepage: https://pub.dev/packages/result_type
- Size: 84 KB
- Stars: 12
- Watchers: 3
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
Awesome Lists containing this project
README
Result Type for Dart
# Content
- [Content](#content)
- [Features](#features)
- [Requirements](#requirements)
- [Install](#install)
- [Example](#example)
- [Support](#support)
- [License](#license)
## Features
Result is a type that represents either [Success](https://github.com/minikin/result_type/blob/main/lib/src/success.dart) or [Failure](https://github.com/minikin/result_type/blob/main/lib/src/failure.dart).
Inspired by [functional programming](https://hackage.haskell.org/package/base-4.12.0.0/docs/Data-Either.html), [Rust](https://doc.rust-lang.org/std/result/enum.Result.html) and [Swift](https://developer.apple.com/documentation/swift/result).
## Requirements
- Dart: 3.3.0+
## Install
```yaml
dependencies:
result_type: ^1.0.0
```
## Example
The detailed example can be found at [result_type/example/example.dart](https://github.com/minikin/result_type/blob/main/example/example.dart).
```dart
import 'dart:math';
import 'package:http/http.dart' as http;
import 'package:result_type/src/result.dart';
import 'imaginary_service.dart';
import 'photo.dart';
import 'photos_service.dart';
final client = http.Client();
final random = Random();
void main() async {
final photosResult = await PhotosService.getPhotos(client);
final photosOr = photosResult.unwrapOr([Photo.initial()]);
print(photosOr);
/// Use `switch` to handle both success and failure.
final _ = switch (photosResult) {
Success(value: final data) => data,
Failure(value: final error) => 'Error: $error'
};
/// Do something with successful operation results or handle an error.
if (photosResult.isSuccess) {
print('Photos Items: ${photosResult.success}');
} else {
print('Error: ${photosResult.failure}');
}
// Chain multiple asynchronous operations.
final result1 = await ImaginaryService.fetchData1();
final result2 = await ImaginaryService.fetchData2(result1.success);
final result3 = await ImaginaryService.fetchData2(result2.success);
// Print the result of the last operation: `Success: Default Data`
print(result3.unwrapOr('Default Data'));
// This will throw an exception as `_handleResult`
// has a case with 'Wrong Data'.
//print(result3.unwrap());
String length(String string) => string.length.toString();
final unwrapOrElse = result3.unwrapOrElse('Default (((((Data)))))', length);
// Print the result of the last operation: `22`
print(unwrapOrElse);
/// Apply transformation to successful operation results or handle an error.
if (photosResult.isSuccess) {
final items = photosResult
.map(
(i) => i.where(
(j) => j.title.length > 60,
),
)
.success;
print('Number of Long Titles: ${items.length}');
} else {
print('Error: ${photosResult.failure}');
}
/// In this example, note the difference in the result of using `map` and
/// `flatMap` with a transformation that returns an result type.
Result getNextInteger() => Success(random.nextInt(4));
Result getNextAfterInteger(int n) =>
Success(random.nextInt(n + 1));
final nextIntegerNestedResults = getNextInteger().map(getNextAfterInteger);
print(nextIntegerNestedResults.runtimeType);
// Prints: Success, dynamic>
final nextIntegerUnboxedResults =
getNextInteger().flatMap(getNextAfterInteger);
print(nextIntegerUnboxedResults.runtimeType);
// Prints: Success
/// Use completion handler / callback style API if you want to.
await PhotosService.getPhotos(client)
..result((photos) {
// print('Photos: $photos');
}, (error) {
print('Error: $error');
});
}
```
To see examples of the following package in action:
```sh
cd example && dart run
```
## Support
Post issues and feature requests on the GitHub [issue tracker](https://github.com/minikin/result_type/issues).
## License
The source code is distributed under the MIT license.
See the [LICENSE](https://github.com/minikin/result_type/blob/main/LICENSE) file for more info.