├── .github ├── ISSUE_TEMPLATE │ ├── bug_report.md │ └── feature_request.md ├── PULL_REQUEST_TEMPLATE.md └── workflows │ └── build.yml ├── .gitignore ├── CHANGELOG.md ├── CODE_OF_CONDUCT.md ├── CONTRIBUTING.md ├── LICENSE ├── README.md ├── analysis_options.yaml ├── example └── example.dart ├── lib ├── result_type.dart └── src │ ├── failure.dart │ ├── result.dart │ └── success.dart ├── pubspec.lock ├── pubspec.yaml └── test ├── failure_test.dart ├── result_test.dart ├── success_test.dart ├── test_all.dart └── utils └── mock_error.dart /.github/ISSUE_TEMPLATE/bug_report.md: -------------------------------------------------------------------------------- 1 | --- 2 | name: Bug report 3 | about: Create a report to help us improve 4 | title: '' 5 | labels: '' 6 | assignees: '' 7 | 8 | --- 9 | 10 | **Describe the bug** 11 | A clear and concise description of what the bug is. 12 | 13 | **To Reproduce** 14 | Steps to reproduce the behavior: 15 | 1. Go to '...' 16 | 2. Click on '....' 17 | 3. Scroll down to '....' 18 | 4. See error 19 | 20 | **Expected behavior** 21 | A clear and concise description of what you expected to happen. 22 | 23 | **Screenshots** 24 | If applicable, add screenshots to help explain your problem. 25 | 26 | **Desktop (please complete the following information):** 27 | - OS: [e.g. iOS] 28 | - Browser [e.g. chrome, safari] 29 | - Version [e.g. 22] 30 | 31 | **Smartphone (please complete the following information):** 32 | - Device: [e.g. iPhone6] 33 | - OS: [e.g. iOS8.1] 34 | - Browser [e.g. stock browser, safari] 35 | - Version [e.g. 22] 36 | 37 | **Additional context** 38 | Add any other context about the problem here. 39 | -------------------------------------------------------------------------------- /.github/ISSUE_TEMPLATE/feature_request.md: -------------------------------------------------------------------------------- 1 | --- 2 | name: Feature request 3 | about: Suggest an idea for this project 4 | title: '' 5 | labels: '' 6 | assignees: '' 7 | 8 | --- 9 | 10 | **Is your feature request related to a problem? Please describe.** 11 | A clear and concise description of what the problem is. Ex. I'm always frustrated when [...] 12 | 13 | **Describe the solution you'd like** 14 | A clear and concise description of what you want to happen. 15 | 16 | **Describe alternatives you've considered** 17 | A clear and concise description of any alternative solutions or features you've considered. 18 | 19 | **Additional context** 20 | Add any other context or screenshots about the feature request here. 21 | -------------------------------------------------------------------------------- /.github/PULL_REQUEST_TEMPLATE.md: -------------------------------------------------------------------------------- 1 | *Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.* 2 | 3 | *List which issues are fixed by this PR. You must list at least one issue.* 4 | 5 | ## Pre-launch Checklist 6 | 7 | - [ ] I read and followed the [Effective Dart](https://dart.dev/guides/language/effective-dart/style). 8 | - [ ] I listed at least one issue or feature that this PR fixes or adds in the description above. 9 | - [ ] I updated/added relevant documentation (doc comments with `///`). 10 | - [ ] I updated/added relevant documentation to README.md. 11 | - [ ] I updated/added relevant code samples to [example](https://github.com/epam-cross-platform-lab/dart_result_type/blob/main/example/example.dart). 12 | - [ ] I added new tests to check the change I am making or feature I am adding, or Minikin said the PR is test-exempt. 13 | - [ ] All existing and new tests are passing. 14 | 15 | If you need help, consider asking for advice on [Twitter](https://twitter.com/minikin). 16 | 17 | Thank you for your contribution 🚀! 18 | -------------------------------------------------------------------------------- /.github/workflows/build.yml: -------------------------------------------------------------------------------- 1 | name: CI 2 | 3 | on: 4 | push: 5 | branches: [ main ] 6 | pull_request: 7 | branches: 8 | - "*" 9 | 10 | jobs: 11 | build: 12 | runs-on: ubuntu-latest 13 | 14 | container: 15 | image: google/dart:latest 16 | 17 | steps: 18 | - uses: actions/checkout@v2 19 | 20 | - name: Print Dart SDK version 21 | run: dart --version 22 | 23 | - name: Install dependencies 24 | run: dart pub get 25 | 26 | - name: Format 27 | run: dart format --set-exit-if-changed lib test example 28 | 29 | - name: Analyze project source 30 | run: dartanalyzer --fatal-infos --fatal-warnings lib test example 31 | 32 | - name: Run example 33 | run: dart run example/example.dart 34 | 35 | - name: Active coverage 36 | run: pub global activate coverage 37 | 38 | - name: Run tests 39 | run: dart test test/test_all.dart 40 | 41 | - name: Start Observatory 42 | run: dart 43 | --disable-service-auth-codes 44 | --enable-vm-service=8111 45 | --pause-isolates-on-exit 46 | --enable-asserts 47 | test/test_all.dart & 48 | 49 | - name: Collect coverage 50 | run: nohup pub global run coverage:collect_coverage 51 | --port=8111 52 | --out=coverage.json 53 | --wait-paused 54 | --resume-isolates 55 | 56 | - name: Format coverage 57 | run: pub global run coverage:format_coverage 58 | --lcov 59 | --in=coverage.json 60 | --out=lcov.info 61 | --packages=.packages 62 | --report-on=lib 63 | 64 | - name: Check Code Coverage 65 | uses: VeryGoodOpenSource/very_good_coverage@v1.1.1 66 | with: 67 | path: lcov.info 68 | min_coverage: 100 69 | 70 | - name: Upload coverage to Codecov 71 | uses: codecov/codecov-action@v1 72 | with: 73 | token: ${{ secrets.CODECOV_TOKEN }} 74 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | # Miscellaneous 2 | *.class 3 | *.log 4 | *.pyc 5 | *.swp 6 | .DS_Store 7 | .atom/ 8 | .buildlog/ 9 | .history 10 | .svn/ 11 | 12 | # IntelliJ related 13 | *.iml 14 | *.ipr 15 | *.iws 16 | .idea/ 17 | 18 | # The .vscode folder contains launch configuration and tasks you configure in 19 | # VS Code which you may wish to be included in version control, so this line 20 | # is commented out by default. 21 | #.vscode/ 22 | 23 | # Flutter/Dart/Pub related 24 | **/doc/api/ 25 | **/ios/Flutter/.last_build_id 26 | .dart_tool/ 27 | .flutter-plugins 28 | .flutter-plugins-dependencies 29 | .packages 30 | .pub-cache/ 31 | .pub/ 32 | doc 33 | /build/ 34 | .buildlog 35 | .dart_tool/ 36 | web/experimental 37 | 38 | # Web related 39 | lib/generated_plugin_registrant.dart 40 | 41 | # Symbolication related 42 | app.*.symbols 43 | 44 | # Obfuscation related 45 | app.*.map.json 46 | 47 | # Android Studio will place build artifacts here 48 | /android/app/debug 49 | /android/app/profile 50 | /android/app/release 51 | 52 | # Or the files created by dart2js. 53 | *.dart.js 54 | *.js_ 55 | *.js.deps 56 | *.js.map 57 | 58 | # Include when developing application packages. 59 | pubspec.lock 60 | coverage* 61 | nohup.out 62 | lcov.info -------------------------------------------------------------------------------- /CHANGELOG.md: -------------------------------------------------------------------------------- 1 | ## [0.1.0] - 04.04.2021. 2 | 3 | - Migrate to NNBD. 4 | 5 | ## 0.0.1 - 20.01.2021 6 | 7 | - Initial Release -------------------------------------------------------------------------------- /CODE_OF_CONDUCT.md: -------------------------------------------------------------------------------- 1 | # Contributor Covenant Code of Conduct 2 | 3 | ## Our Pledge 4 | 5 | In the interest of fostering an open and welcoming environment, we as 6 | contributors and maintainers pledge to making participation in our project and 7 | our community a harassment-free experience for everyone, regardless of age, body 8 | size, disability, ethnicity, sex characteristics, gender identity and expression, 9 | level of experience, education, socio-economic status, nationality, personal 10 | appearance, race, religion, or sexual identity and orientation. 11 | 12 | ## Our Standards 13 | 14 | Examples of behavior that contributes to creating a positive environment 15 | include: 16 | 17 | * Using welcoming and inclusive language 18 | * Being respectful of differing viewpoints and experiences 19 | * Gracefully accepting constructive criticism 20 | * Focusing on what is best for the community 21 | * Showing empathy towards other community members 22 | 23 | Examples of unacceptable behavior by participants include: 24 | 25 | * The use of sexualized language or imagery and unwelcome sexual attention or 26 | advances 27 | * Trolling, insulting/derogatory comments, and personal or political attacks 28 | * Public or private harassment 29 | * Publishing others' private information, such as a physical or electronic 30 | address, without explicit permission 31 | * Other conduct which could reasonably be considered inappropriate in a 32 | professional setting 33 | 34 | ## Our Responsibilities 35 | 36 | Project maintainers are responsible for clarifying the standards of acceptable 37 | behavior and are expected to take appropriate and fair corrective action in 38 | response to any instances of unacceptable behavior. 39 | 40 | Project maintainers have the right and responsibility to remove, edit, or 41 | reject comments, commits, code, wiki edits, issues, and other contributions 42 | that are not aligned to this Code of Conduct, or to ban temporarily or 43 | permanently any contributor for other behaviors that they deem inappropriate, 44 | threatening, offensive, or harmful. 45 | 46 | ## Scope 47 | 48 | This Code of Conduct applies both within project spaces and in public spaces 49 | when an individual is representing the project or its community. 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The project team is 61 | obligated to maintain confidentiality with regard to the reporter of an incident. 62 | Further details of specific enforcement policies may be posted separately. 63 | 64 | Project maintainers who do not follow or enforce the Code of Conduct in good 65 | faith may face temporary or permanent repercussions as determined by other 66 | members of the project's leadership. 67 | 68 | ## Attribution 69 | 70 | This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4, 71 | available at https://www.contributor-covenant.org/version/1/4/code-of-conduct.html 72 | 73 | [homepage]: https://www.contributor-covenant.org 74 | 75 | For answers to common questions about this code of conduct, see 76 | https://www.contributor-covenant.org/faq 77 | -------------------------------------------------------------------------------- /CONTRIBUTING.md: -------------------------------------------------------------------------------- 1 | # Contributing 2 | 3 | When contributing to this repository, please first discuss the change you wish to make via issue, 4 | email, or any other method with the owners of this repository before making a change. 5 | 6 | Please note we have a code of conduct, please follow it in all your interactions with the project. 7 | 8 | ## Pull Request Process 9 | 10 | 1. Ensure any install or build dependencies are removed before the end of the layer when doing a 11 | build. 12 | 2. Update the README.md with details of changes to the interface, this includes new environment 13 | variables, exposed ports, useful file locations and container parameters. 14 | 3. Increase the version numbers in any examples files and the README.md to the new version that this 15 | Pull Request would represent. The versioning scheme we use is [SemVer](http://semver.org/). 16 | 4. You may merge the Pull Request in once you have the sign-off of two other developers, or if you 17 | do not have permission to do that, you may request the second reviewer to merge it for you. 18 | 19 | ## Code of Conduct 20 | 21 | ### Our Pledge 22 | 23 | In the interest of fostering an open and welcoming environment, we as 24 | contributors and maintainers pledge to making participation in our project and 25 | our community a harassment-free experience for everyone, regardless of age, body 26 | size, disability, ethnicity, gender identity and expression, level of experience, 27 | nationality, personal appearance, race, religion, or sexual identity and 28 | orientation. 29 | 30 | ### Our Standards 31 | 32 | Examples of behavior that contributes to creating a positive environment 33 | include: 34 | 35 | * Using welcoming and inclusive language 36 | * Being respectful of differing viewpoints and experiences 37 | * Gracefully accepting constructive criticism 38 | * Focusing on what is best for the community 39 | * Showing empathy towards other community members 40 | 41 | Examples of unacceptable behavior by participants include: 42 | 43 | * The use of sexualized language or imagery and unwelcome sexual attention or 44 | advances 45 | * Trolling, insulting/derogatory comments, and personal or political attacks 46 | * Public or private harassment 47 | * Publishing others' private information, such as a physical or electronic 48 | address, without explicit permission 49 | * Other conduct which could reasonably be considered inappropriate in a 50 | professional setting 51 | 52 | ### Our Responsibilities 53 | 54 | Project maintainers are responsible for clarifying the standards of acceptable 55 | behavior and are expected to take appropriate and fair corrective action in 56 | response to any instances of unacceptable behavior. 57 | 58 | Project maintainers have the right and responsibility to remove, edit, or 59 | reject comments, commits, code, wiki edits, issues, and other contributions 60 | that are not aligned to this Code of Conduct, or to ban temporarily or 61 | permanently any contributor for other behaviors that they deem inappropriate, 62 | threatening, offensive, or harmful. 63 | 64 | ### Scope 65 | 66 | This Code of Conduct applies both within project spaces and in public spaces 67 | when an individual is representing the project or its community. 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Result Type for Dart

2 | 3 |

4 | 5 | CI Status 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | Result Type is released under the Apache license. 14 | 15 | 16 | 17 | Effective Dart 18 | 19 | 20 | 21 | PRs welcome! 22 | 23 |

24 | 25 | # Content 26 | 27 | - [Features](#features) 28 | - [Requirements](#requirements) 29 | - [Install](#install) 30 | - [Example](#example) 31 | - [Support](#support) 32 | - [License](#license) 33 | 34 | ## Features 35 | 36 | Result is a type that represents either [Success](https://github.com/epam-cross-platform-lab/dart_result_type/blob/main/lib/src/success.dart) or [Failure](https://github.com/epam-cross-platform-lab/dart_result_type/blob/main/lib/src/failure.dart). 37 | 38 | Inspired by [functional programming](http://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). 39 | 40 | ## Requirements 41 | 42 | - Dart: 2.12.0+ 43 | 44 | ## Install 45 | 46 | ```yaml 47 | dependencies: 48 | result_type: ^0.1.0 49 | ``` 50 | 51 | ## Example 52 | 53 | The detailed example can be found at [result_type/example/example.dart](https://github.com/epam-cross-platform-lab/dart_result_type/blob/main/example/example.dart). 54 | 55 | ```dart 56 | import 'dart:async'; 57 | import 'dart:convert'; 58 | import 'dart:math'; 59 | 60 | import 'package:http/http.dart' as http; 61 | import 'package:result_type/result_type.dart'; 62 | 63 | void main() async { 64 | final random = Random(); 65 | final client = http.Client(); 66 | final result = await getPhotos(client); 67 | 68 | /// Do something with successful operation results or handle an error. 69 | if (result.isSuccess) { 70 | print('Photos Items: ${result.success}'); 71 | } else { 72 | print('Error: ${result.failure}'); 73 | } 74 | 75 | /// Apply transformation to successful operation results or handle an error. 76 | if (result.isSuccess) { 77 | final items = result.map((i) => i.where((j) => j.title.length > 60)).success; 78 | print('Number of Long Titles: ${items.length}'); 79 | } else { 80 | print('Error: ${result.failure}'); 81 | } 82 | 83 | /// In this example, note the difference in the result of using `map` and 84 | /// `flatMap` with a transformation that returns an result type. 85 | Result getNextInteger() => Success(random.nextInt(4)); 86 | Result getNextAfterInteger(int n) => Success(random.nextInt(n + 1)); 87 | 88 | final nextIntegerNestedResults = getNextInteger().map(getNextAfterInteger); 89 | print(nextIntegerNestedResults.runtimeType); 90 | /// `Prints`: Success, dynamic> 91 | 92 | final nextIntegerUnboxedResults = getNextInteger().flatMap(getNextAfterInteger); 93 | print(nextIntegerUnboxedResults.runtimeType); 94 | /// `Prints`: Success 95 | 96 | /// Use completion handler / callback style API if you want to. 97 | await getPhotos(client) 98 | ..result((photos) { 99 | print('Photos: $photos'); 100 | }, (error) { 101 | print('Error: $error'); 102 | }); 103 | } 104 | ``` 105 | 106 | To see examples of the following package in action: 107 | 108 | ```sh 109 | cd example && dart run 110 | ``` 111 | 112 | ## Support 113 | 114 | Post issues and feature requests on the GitHub [issue tracker](https://github.com/epam-cross-platform-lab/dart_result_type/issues). 115 | 116 | ## License 117 | 118 | The source code of Result Type project is available under the Apache license. 119 | See the [LICENSE](https://github.com/epam-cross-platform-lab/dart_result_type/blob/main/LICENSE) file for more info. 120 | -------------------------------------------------------------------------------- /analysis_options.yaml: -------------------------------------------------------------------------------- 1 | analyzer: 2 | language: 3 | strict-inference: true 4 | strict-raw-types: true 5 | errors: 6 | always_put_required_named_parameters_first: error 7 | avoid_relative_lib_imports: error 8 | missing_required_param: error 9 | no_duplicate_case_values: error 10 | prefer_const_constructors: error 11 | 12 | linter: 13 | rules: 14 | - avoid_shadowing_type_parameters 15 | - avoid_private_typedef_functions 16 | - avoid_returning_null 17 | - avoid_setters_without_getters 18 | - await_only_futures 19 | - camel_case_types 20 | - cancel_subscriptions 21 | - close_sinks 22 | - constant_identifier_names 23 | - control_flow_in_finally 24 | - directives_ordering 25 | - empty_constructor_bodies 26 | - empty_statements 27 | - hash_and_equals 28 | - implementation_imports 29 | - lines_longer_than_80_chars 30 | - non_constant_identifier_names 31 | - one_member_abstracts 32 | - package_names 33 | - package_prefixed_library_names 34 | - prefer_collection_literals 35 | - prefer_const_constructors 36 | - prefer_final_locals 37 | - prefer_function_declarations_over_variables 38 | - prefer_if_elements_to_conditional_expressions 39 | - prefer_interpolation_to_compose_strings 40 | - prefer_null_aware_operators 41 | - prefer_typing_uninitialized_variables 42 | - test_types_in_equals 43 | - type_annotate_public_apis 44 | - unnecessary_await_in_return 45 | - unnecessary_brace_in_string_interps 46 | - unnecessary_const 47 | - unnecessary_getters_setters 48 | - unnecessary_parenthesis 49 | - unnecessary_statements 50 | - use_to_and_as_if_applicable 51 | # Effective Dart Rules 52 | - avoid_catches_without_on_clauses 53 | - avoid_catching_errors 54 | - avoid_classes_with_only_static_members 55 | - avoid_equals_and_hash_code_on_mutable_classes 56 | - avoid_function_literals_in_foreach_calls 57 | - avoid_init_to_null 58 | - avoid_null_checks_in_equality_operators 59 | - avoid_positional_boolean_parameters 60 | - avoid_relative_lib_imports 61 | - avoid_return_types_on_setters 62 | - avoid_returning_this 63 | - avoid_types_on_closure_parameters 64 | - camel_case_extensions 65 | - curly_braces_in_flow_control_structures 66 | - file_names 67 | - library_names 68 | - library_prefixes 69 | - omit_local_variable_types 70 | - package_api_docs 71 | - prefer_adjacent_string_concatenation 72 | - prefer_equal_for_default_values 73 | - prefer_final_fields 74 | - prefer_generic_function_type_aliases 75 | - prefer_initializing_formals 76 | - prefer_is_empty 77 | - prefer_is_not_empty 78 | - prefer_iterable_whereType 79 | - prefer_mixin 80 | - prefer_relative_imports 81 | # - public_member_api_docs 82 | - slash_for_doc_comments 83 | - type_init_formals 84 | - unnecessary_lambdas 85 | - unnecessary_new 86 | - unnecessary_this 87 | - use_setters_to_change_properties -------------------------------------------------------------------------------- /example/example.dart: -------------------------------------------------------------------------------- 1 | import 'dart:async'; 2 | import 'dart:convert'; 3 | import 'dart:math'; 4 | 5 | import 'package:http/http.dart' as http; 6 | import 'package:result_type/result_type.dart'; 7 | 8 | void main() async { 9 | final random = Random(); 10 | final client = http.Client(); 11 | final result = await getPhotos(client); 12 | 13 | /// Do something with successful operation results or handle an error. 14 | if (result.isSuccess) { 15 | print('Photos Items: ${result.success}'); 16 | } else { 17 | print('Error: ${result.failure}'); 18 | } 19 | 20 | /// Apply transformation to successful operation results or handle an error. 21 | if (result.isSuccess) { 22 | final items = 23 | result.map((i) => i.where((j) => j.title.length > 60)).success; 24 | print('Number of Long Titles: ${items.length}'); 25 | } else { 26 | print('Error: ${result.failure}'); 27 | } 28 | 29 | /// In this example, note the difference in the result of using `map` and 30 | /// `flatMap` with a transformation that returns an result type. 31 | Result getNextInteger() => Success(random.nextInt(4)); 32 | Result getNextAfterInteger(int n) => 33 | Success(random.nextInt(n + 1)); 34 | 35 | final nextIntegerNestedResults = getNextInteger().map(getNextAfterInteger); 36 | print(nextIntegerNestedResults.runtimeType); 37 | // Prints: Success, dynamic> 38 | 39 | final nextIntegerUnboxedResults = 40 | getNextInteger().flatMap(getNextAfterInteger); 41 | print(nextIntegerUnboxedResults.runtimeType); 42 | // Prints: Success 43 | 44 | /// Use completion handler / callback style API if you want to. 45 | await getPhotos(client) 46 | ..result((photos) { 47 | print('Photos: $photos'); 48 | }, (error) { 49 | print('Error: $error'); 50 | }); 51 | } 52 | 53 | class Photo { 54 | final int id; 55 | final String title; 56 | final String thumbnailUrl; 57 | 58 | const Photo({ 59 | required this.id, 60 | required this.title, 61 | required this.thumbnailUrl, 62 | }); 63 | 64 | factory Photo.fromJson(Map json) { 65 | print(json); 66 | return Photo( 67 | id: json['id'] as int, 68 | title: json['title'] as String, 69 | thumbnailUrl: json['thumbnailUrl'] as String, 70 | ); 71 | } 72 | 73 | @override 74 | String toString() => 75 | 'Photo(id: $id, title: $title, thumbnailUrl: $thumbnailUrl)'; 76 | } 77 | 78 | extension PhotoExtension on Photo { 79 | static List parsePhotos(String responseBody) { 80 | final jsonObject = jsonDecode(responseBody) as Iterable; 81 | return jsonObject 82 | .map((json) => Photo.fromJson(Map.from(json))) 83 | .toList(); 84 | } 85 | } 86 | 87 | class NetworkError implements Exception { 88 | final int code; 89 | final String description; 90 | 91 | const NetworkError({ 92 | required this.code, 93 | required this.description, 94 | }); 95 | 96 | @override 97 | String toString() => 'NetworkError(code: $code, description: $description)'; 98 | 99 | static const notFound = NetworkError(code: 404, description: 'Not Found'); 100 | } 101 | 102 | Future, NetworkError>> getPhotos(http.Client client) async { 103 | const path = 'https://jsonplaceholder.typicode.com/photos'; 104 | try { 105 | final jsonString = await client.get(Uri.parse(path)); 106 | return Success(PhotoExtension.parsePhotos(jsonString.body)); 107 | } on NetworkError catch (_) { 108 | return Failure(NetworkError.notFound); 109 | } 110 | } 111 | -------------------------------------------------------------------------------- /lib/result_type.dart: -------------------------------------------------------------------------------- 1 | export 'src/failure.dart'; 2 | export 'src/result.dart'; 3 | export 'src/success.dart'; 4 | -------------------------------------------------------------------------------- /lib/src/failure.dart: -------------------------------------------------------------------------------- 1 | import 'package:meta/meta.dart'; 2 | 3 | import 'result.dart'; 4 | 5 | /// A failure, storing a [Failure] value. 6 | @immutable 7 | class Failure extends Result { 8 | final F value; 9 | 10 | Failure(this.value); 11 | 12 | @override 13 | bool operator ==(Object o) { 14 | if (identical(this, o)) return true; 15 | 16 | return o is Failure && o.value == value; 17 | } 18 | 19 | @override 20 | int get hashCode => value.hashCode; 21 | 22 | @override 23 | String toString() => 'Failure: $value'; 24 | } 25 | -------------------------------------------------------------------------------- /lib/src/result.dart: -------------------------------------------------------------------------------- 1 | // ignore_for_file: lines_longer_than_80_chars, avoid_shadowing_type_parameters 2 | import 'failure.dart'; 3 | import 'success.dart'; 4 | 5 | /// Callbacks that return [Success] or [Failure]. 6 | typedef Completion = void Function(T value); 7 | 8 | /// A value that represents either a success or a failure, including an 9 | /// associated value in each case. 10 | abstract class Result { 11 | /// Returns true if [Result] is [Failure]. 12 | bool get isFailure => this is Failure; 13 | 14 | /// Returns true if [Result] is [Success]. 15 | bool get isSuccess => this is Success; 16 | 17 | /// Returns a new value of [Failure] result. 18 | /// 19 | /// Handle an error or do something with successful operation results: 20 | /// 21 | /// ```dart 22 | /// final result = await getPhotos(); 23 | /// 24 | /// if (result.isFailure) { 25 | /// print('Error: ${result.failure}'); 26 | /// } else { 27 | /// print('Photos Items: ${result.success}'); 28 | /// } 29 | /// ``` 30 | /// 31 | F get failure { 32 | if (this is Failure) { 33 | return (this as Failure).value; 34 | } 35 | 36 | throw Exception( 37 | 'Make sure that result [isFailure] before accessing [failure]', 38 | ); 39 | } 40 | 41 | /// Returns a new value of [Success] result. 42 | /// 43 | /// Do something with successful operation results or handle an error: 44 | /// 45 | /// ```dart 46 | /// final result = await getPhotos(); 47 | /// 48 | /// if (result.isSuccess) { 49 | /// print('Photos Items: ${result.success}'); 50 | /// } else { 51 | /// print('Error: ${result.failure}'); 52 | /// } 53 | /// ``` 54 | /// 55 | S get success { 56 | if (this is Success) { 57 | return (this as Success).value; 58 | } 59 | 60 | throw Exception( 61 | 'Make sure that result [isSuccess] before accessing [success]', 62 | ); 63 | } 64 | 65 | /// Returns a new value of [Result] from closure 66 | /// either a success or a failure. 67 | /// 68 | /// This example shows how to use completion handler. 69 | /// 70 | /// ```dart 71 | /// final result = await getPhotos(); 72 | /// 73 | /// await getPhotos(client) 74 | /// ..result((photos) { 75 | /// print('Photos: $photos'); 76 | /// }, (error) { 77 | /// print('Error: $error'); 78 | /// }); 79 | /// ``` 80 | /// 81 | void result(Completion success, Completion failure) { 82 | if (isSuccess) { 83 | final left = this as Success; 84 | success(left.value); 85 | } 86 | 87 | if (isFailure) { 88 | final right = this as Failure; 89 | failure(right.value); 90 | } 91 | } 92 | 93 | /// Maps a [Result] to [Result] by applying a function 94 | /// to a contained [Success] value, leaving an [Failure] value untouched. 95 | /// This function can be used to compose the results of two functions. 96 | /// 97 | /// Apply transformation to successful operation results or handle an error: 98 | /// 99 | /// ```dart 100 | /// final result = await getPhotos(); 101 | /// 102 | /// if (result.isSuccess) { 103 | /// final items = result.map((i) => i.where((j) => j.title.length > 60)).success; 104 | /// print('Number of Long Titles: ${items.length}'); 105 | /// } else { 106 | /// print('Error: ${result.failure}'); 107 | /// } 108 | /// ``` 109 | /// 110 | Result map(U Function(S) transform) { 111 | if (isSuccess) { 112 | final left = this as Success; 113 | return Success(transform(left.value)); 114 | } else { 115 | final right = this as Failure; 116 | return Failure(right.value); 117 | } 118 | } 119 | 120 | /// Maps a [Result] to [Result] by applying a function 121 | /// to a contained [Failure] value, leaving an [Success] value untouched. 122 | /// 123 | /// This function can be used to pass through a successful result 124 | /// while applying transformation to [Failure]. 125 | /// 126 | Result mapError(E Function(F) transform) { 127 | if (isSuccess) { 128 | final left = this as Success; 129 | return Success(left.value); 130 | } else { 131 | final right = this as Failure; 132 | return Failure(transform(right.value)); 133 | } 134 | } 135 | 136 | /// Maps a [Result] to [Result] by applying a function 137 | /// to a contained [Success] value and unwrapping the produced result, 138 | /// leaving an [Failure] value untouched. 139 | /// 140 | /// Use this method to avoid a nested result when your transformation 141 | /// produces another [Result] type. 142 | /// 143 | /// In this example, note the difference in the result of using `map` and 144 | /// `flatMap` with a transformation that returns an result type. 145 | /// 146 | /// ```dart 147 | /// Result getNextInteger() => Success(random.nextInt(4)); 148 | /// Result getNextAfterInteger(int n) => Success(random.nextInt(n + 1)); 149 | /// 150 | /// final nextIntegerNestedResults = getNextInteger().map(getNextAfterInteger); 151 | /// print(nextIntegerNestedResults.runtimeType); 152 | /// `Prints: Success, dynamic>` 153 | /// 154 | /// final nextIntegerUnboxedResults = getNextInteger().flatMap(getNextAfterInteger); 155 | /// print(nextIntegerUnboxedResults.runtimeType); 156 | /// `Prints: Success` 157 | /// ``` 158 | Result flatMap(Result Function(S) transform) { 159 | if (isSuccess) { 160 | final left = this as Success; 161 | return transform(left.value); 162 | } else { 163 | final right = this as Failure; 164 | return Failure(right.value); 165 | } 166 | } 167 | 168 | /// Maps a [Result] to [Result] by applying a function 169 | /// to a contained [Failure] value, leaving an [Success] value untouched. 170 | /// 171 | /// This function can be used to pass through a successful result 172 | /// while unboxing [Failure] and applying transformation to it. 173 | /// 174 | Result flatMapError(Result Function(F) transform) { 175 | if (isSuccess) { 176 | final left = this as Success; 177 | return Success(left.value); 178 | } else { 179 | final right = this as Failure; 180 | return transform(right.value); 181 | } 182 | } 183 | } 184 | -------------------------------------------------------------------------------- /lib/src/success.dart: -------------------------------------------------------------------------------- 1 | import 'package:meta/meta.dart'; 2 | 3 | import 'result.dart'; 4 | 5 | /// A success, storing a [Success] value. 6 | @immutable 7 | class Success extends Result { 8 | final S value; 9 | 10 | Success(this.value); 11 | 12 | @override 13 | bool operator ==(Object o) { 14 | if (identical(this, o)) return true; 15 | 16 | return o is Success && o.value == value; 17 | } 18 | 19 | @override 20 | int get hashCode => value.hashCode; 21 | 22 | @override 23 | String toString() => 'Success: $value'; 24 | } 25 | -------------------------------------------------------------------------------- /pubspec.lock: -------------------------------------------------------------------------------- 1 | # Generated by pub 2 | # See https://dart.dev/tools/pub/glossary#lockfile 3 | packages: 4 | _fe_analyzer_shared: 5 | dependency: transitive 6 | description: 7 | name: _fe_analyzer_shared 8 | url: "https://pub.dartlang.org" 9 | source: hosted 10 | version: "19.0.0" 11 | analyzer: 12 | dependency: transitive 13 | description: 14 | name: analyzer 15 | url: "https://pub.dartlang.org" 16 | source: hosted 17 | version: "1.3.0" 18 | args: 19 | dependency: transitive 20 | description: 21 | name: args 22 | url: "https://pub.dartlang.org" 23 | source: hosted 24 | version: "2.0.0" 25 | async: 26 | dependency: transitive 27 | description: 28 | name: async 29 | url: "https://pub.dartlang.org" 30 | source: hosted 31 | version: "2.5.0" 32 | boolean_selector: 33 | dependency: transitive 34 | description: 35 | name: boolean_selector 36 | url: "https://pub.dartlang.org" 37 | source: hosted 38 | version: "2.1.0" 39 | charcode: 40 | dependency: transitive 41 | description: 42 | name: charcode 43 | url: "https://pub.dartlang.org" 44 | source: hosted 45 | version: "1.2.0" 46 | cli_util: 47 | dependency: transitive 48 | description: 49 | name: cli_util 50 | url: "https://pub.dartlang.org" 51 | source: hosted 52 | version: "0.3.0" 53 | collection: 54 | dependency: transitive 55 | description: 56 | name: collection 57 | url: "https://pub.dartlang.org" 58 | source: hosted 59 | version: "1.15.0" 60 | convert: 61 | dependency: transitive 62 | description: 63 | name: convert 64 | url: "https://pub.dartlang.org" 65 | source: hosted 66 | version: "3.0.0" 67 | coverage: 68 | dependency: transitive 69 | description: 70 | name: coverage 71 | url: "https://pub.dartlang.org" 72 | source: hosted 73 | version: "1.0.2" 74 | crypto: 75 | dependency: transitive 76 | description: 77 | name: crypto 78 | url: "https://pub.dartlang.org" 79 | source: hosted 80 | version: "3.0.1" 81 | file: 82 | dependency: transitive 83 | description: 84 | name: file 85 | url: "https://pub.dartlang.org" 86 | source: hosted 87 | version: "6.1.0" 88 | glob: 89 | dependency: transitive 90 | description: 91 | name: glob 92 | url: "https://pub.dartlang.org" 93 | source: hosted 94 | version: "2.0.1" 95 | http: 96 | dependency: "direct dev" 97 | description: 98 | name: http 99 | url: "https://pub.dartlang.org" 100 | source: hosted 101 | version: "0.13.1" 102 | http_multi_server: 103 | dependency: transitive 104 | description: 105 | name: http_multi_server 106 | url: "https://pub.dartlang.org" 107 | source: hosted 108 | version: "3.0.0" 109 | http_parser: 110 | dependency: transitive 111 | description: 112 | name: http_parser 113 | url: "https://pub.dartlang.org" 114 | source: hosted 115 | version: "4.0.0" 116 | io: 117 | dependency: transitive 118 | description: 119 | name: io 120 | url: "https://pub.dartlang.org" 121 | source: hosted 122 | version: "1.0.0" 123 | js: 124 | dependency: transitive 125 | description: 126 | name: js 127 | url: "https://pub.dartlang.org" 128 | source: hosted 129 | version: "0.6.3" 130 | logging: 131 | dependency: transitive 132 | description: 133 | name: logging 134 | url: "https://pub.dartlang.org" 135 | source: hosted 136 | version: "1.0.1" 137 | matcher: 138 | dependency: transitive 139 | description: 140 | name: matcher 141 | url: "https://pub.dartlang.org" 142 | source: hosted 143 | version: "0.12.10" 144 | meta: 145 | dependency: "direct main" 146 | description: 147 | name: meta 148 | url: "https://pub.dartlang.org" 149 | source: hosted 150 | version: "1.3.0" 151 | mime: 152 | dependency: transitive 153 | description: 154 | name: mime 155 | url: "https://pub.dartlang.org" 156 | source: hosted 157 | version: "1.0.0" 158 | node_preamble: 159 | dependency: transitive 160 | description: 161 | name: node_preamble 162 | url: "https://pub.dartlang.org" 163 | source: hosted 164 | version: "2.0.0" 165 | package_config: 166 | dependency: transitive 167 | description: 168 | name: package_config 169 | url: "https://pub.dartlang.org" 170 | source: hosted 171 | version: "2.0.0" 172 | path: 173 | dependency: transitive 174 | description: 175 | name: path 176 | url: "https://pub.dartlang.org" 177 | source: hosted 178 | version: "1.8.0" 179 | pedantic: 180 | dependency: transitive 181 | description: 182 | name: pedantic 183 | url: "https://pub.dartlang.org" 184 | source: hosted 185 | version: "1.11.0" 186 | pool: 187 | dependency: transitive 188 | description: 189 | name: pool 190 | url: "https://pub.dartlang.org" 191 | source: hosted 192 | version: "1.5.0" 193 | pub_semver: 194 | dependency: transitive 195 | description: 196 | name: pub_semver 197 | url: "https://pub.dartlang.org" 198 | source: hosted 199 | version: "2.0.0" 200 | shelf: 201 | dependency: transitive 202 | description: 203 | name: shelf 204 | url: "https://pub.dartlang.org" 205 | source: hosted 206 | version: "1.1.0" 207 | shelf_packages_handler: 208 | dependency: transitive 209 | description: 210 | name: shelf_packages_handler 211 | url: "https://pub.dartlang.org" 212 | source: hosted 213 | version: "3.0.0" 214 | shelf_static: 215 | dependency: transitive 216 | description: 217 | name: shelf_static 218 | url: "https://pub.dartlang.org" 219 | source: hosted 220 | version: "1.0.0" 221 | shelf_web_socket: 222 | dependency: transitive 223 | description: 224 | name: shelf_web_socket 225 | url: "https://pub.dartlang.org" 226 | source: hosted 227 | version: "1.0.1" 228 | source_map_stack_trace: 229 | dependency: transitive 230 | description: 231 | name: source_map_stack_trace 232 | url: "https://pub.dartlang.org" 233 | source: hosted 234 | version: "2.1.0" 235 | source_maps: 236 | dependency: transitive 237 | description: 238 | name: source_maps 239 | url: "https://pub.dartlang.org" 240 | source: hosted 241 | version: "0.10.10" 242 | source_span: 243 | dependency: transitive 244 | description: 245 | name: source_span 246 | url: "https://pub.dartlang.org" 247 | source: hosted 248 | version: "1.8.1" 249 | stack_trace: 250 | dependency: transitive 251 | description: 252 | name: stack_trace 253 | url: "https://pub.dartlang.org" 254 | source: hosted 255 | version: "1.10.0" 256 | stream_channel: 257 | dependency: transitive 258 | description: 259 | name: stream_channel 260 | url: "https://pub.dartlang.org" 261 | source: hosted 262 | version: "2.1.0" 263 | string_scanner: 264 | dependency: transitive 265 | description: 266 | name: string_scanner 267 | url: "https://pub.dartlang.org" 268 | source: hosted 269 | version: "1.1.0" 270 | term_glyph: 271 | dependency: transitive 272 | description: 273 | name: term_glyph 274 | url: "https://pub.dartlang.org" 275 | source: hosted 276 | version: "1.2.0" 277 | test: 278 | dependency: "direct dev" 279 | description: 280 | name: test 281 | url: "https://pub.dartlang.org" 282 | source: hosted 283 | version: "1.16.8" 284 | test_api: 285 | dependency: transitive 286 | description: 287 | name: test_api 288 | url: "https://pub.dartlang.org" 289 | source: hosted 290 | version: "0.3.0" 291 | test_core: 292 | dependency: transitive 293 | description: 294 | name: test_core 295 | url: "https://pub.dartlang.org" 296 | source: hosted 297 | version: "0.3.19" 298 | typed_data: 299 | dependency: transitive 300 | description: 301 | name: typed_data 302 | url: "https://pub.dartlang.org" 303 | source: hosted 304 | version: "1.3.0" 305 | vm_service: 306 | dependency: transitive 307 | description: 308 | name: vm_service 309 | url: "https://pub.dartlang.org" 310 | source: hosted 311 | version: "6.2.0" 312 | watcher: 313 | dependency: transitive 314 | description: 315 | name: watcher 316 | url: "https://pub.dartlang.org" 317 | source: hosted 318 | version: "1.0.0" 319 | web_socket_channel: 320 | dependency: transitive 321 | description: 322 | name: web_socket_channel 323 | url: "https://pub.dartlang.org" 324 | source: hosted 325 | version: "2.0.0" 326 | webkit_inspection_protocol: 327 | dependency: transitive 328 | description: 329 | name: webkit_inspection_protocol 330 | url: "https://pub.dartlang.org" 331 | source: hosted 332 | version: "1.0.0" 333 | yaml: 334 | dependency: transitive 335 | description: 336 | name: yaml 337 | url: "https://pub.dartlang.org" 338 | source: hosted 339 | version: "3.1.0" 340 | sdks: 341 | dart: ">=2.12.0 <3.0.0" 342 | -------------------------------------------------------------------------------- /pubspec.yaml: -------------------------------------------------------------------------------- 1 | name: result_type 2 | version: 0.1.0 3 | description: Result Type represents either a success or a failure, including an associated value in each case. 4 | repository: https://github.com/epam-cross-platform-lab/dart_result_type 5 | 6 | environment: 7 | sdk: ">=2.12.0 <3.0.0" 8 | 9 | dependencies: 10 | meta: ^1.3.0 11 | 12 | dev_dependencies: 13 | http: ^0.13.1 14 | test: ^1.16.8 -------------------------------------------------------------------------------- /test/failure_test.dart: -------------------------------------------------------------------------------- 1 | import 'package:result_type/src/failure.dart'; 2 | import 'package:test/test.dart'; 3 | 4 | import 'utils/mock_error.dart'; 5 | 6 | void main() { 7 | group('Failure', () { 8 | test('Should return _TestError', () { 9 | final failure = Failure(const MockError(1)); 10 | expect(failure.value.code, 1); 11 | }); 12 | 13 | test('Two identical Failures should be equal', () { 14 | final failure1 = Failure(const MockError(1)); 15 | final failure2 = Failure(const MockError(1)); 16 | 17 | expect(failure1, failure2); 18 | }); 19 | 20 | test('Two identical Failures should have the same hashCode', () { 21 | final failure1 = Failure(const MockError(1)); 22 | final failure2 = Failure(const MockError(1)); 23 | 24 | expect(failure1.hashCode, failure2.hashCode); 25 | }); 26 | 27 | test('Can print to string', () { 28 | final failure = Failure(const MockError(1)); 29 | expect(failure.toString(), 'Failure: MockError(code: 1)'); 30 | }); 31 | }); 32 | } 33 | -------------------------------------------------------------------------------- /test/result_test.dart: -------------------------------------------------------------------------------- 1 | import 'dart:math'; 2 | 3 | import 'package:result_type/result_type.dart'; 4 | import 'package:test/test.dart'; 5 | 6 | import 'utils/mock_error.dart'; 7 | 8 | void main() { 9 | group('Result:', () { 10 | Random? random; 11 | 12 | setUp(() { 13 | random = Random(); 14 | }); 15 | 16 | tearDown(() { 17 | random = null; 18 | }); 19 | 20 | test('Returns Success', () { 21 | final result = getUser(value: true); 22 | if (result.isSuccess) { 23 | print('Success: ${result.success}'); 24 | } else { 25 | print('Error: ${result.failure}'); 26 | } 27 | 28 | expect(result.success, 'John Doe'); 29 | }); 30 | 31 | test('Returns Failure', () { 32 | final result = getUser(value: false); 33 | if (result.isSuccess) { 34 | print('Success: ${result.success}'); 35 | } else { 36 | print('Error: ${result.failure}'); 37 | } 38 | 39 | expect(result.failure, const MockError(404)); 40 | }); 41 | 42 | test('Returns Success From Callbacks', () { 43 | getUser(value: true) 44 | ..result((success) { 45 | expect(success, 'John Doe'); 46 | }, (_) {}); 47 | }); 48 | 49 | test('Returns Failure From Callbacks', () { 50 | getUser(value: false) 51 | ..result((_) {}, (error) { 52 | expect(error, const MockError(404)); 53 | }); 54 | }); 55 | 56 | test( 57 | '''Throw Exception when accessing success value without checking if isSuccess''', 58 | () { 59 | final result = getUser(value: false); 60 | 61 | expect(() => result.success, throwsException); 62 | }); 63 | 64 | test( 65 | '''Throw Exception when accessing failure value without checking if isFailure''', 66 | () { 67 | final result = getUser(value: true); 68 | 69 | expect(() => result.failure, throwsException); 70 | }); 71 | 72 | test('Apply map transformation to successful operation results', () { 73 | final result = getUser(value: true); 74 | final user = result.map((i) => i.toUpperCase()).success; 75 | 76 | expect(user, 'JOHN DOE'); 77 | }); 78 | 79 | test( 80 | '''Throw an error from map transformation without applying transformation to error type''', 81 | () { 82 | final result = getUser(value: false); 83 | final error = result.map((i) => i.toUpperCase()).failure; 84 | 85 | expect(error, const MockError(404)); 86 | }); 87 | 88 | test('Apply mapError transformation to failure type', () { 89 | final error = 90 | getUser(value: false).mapError((i) => MockError(i.code - 4)).failure; 91 | 92 | expect(error.code, const MockError(400).code); 93 | }); 94 | 95 | test( 96 | '''Returns successful result without applying mapError transformation''', 97 | () { 98 | final maybeError = 99 | getUser(value: true).mapError((i) => MockError(i.code - 4)); 100 | 101 | if (maybeError.isFailure) { 102 | } else { 103 | expect(maybeError.success, 'John Doe'); 104 | } 105 | }); 106 | 107 | test('Apply flatMap transformation to successful operation results', () { 108 | Result getNextInteger() => Success(random!.nextInt(4)); 109 | Result getNextAfterInteger(int n) => 110 | Success(random!.nextInt(n + 1)); 111 | 112 | final nextIntegerUnboxedResults = 113 | getNextInteger().flatMap(getNextAfterInteger); 114 | 115 | expect( 116 | nextIntegerUnboxedResults, 117 | const TypeMatcher>(), 118 | ); 119 | }); 120 | 121 | test('flatMap does not apply transformation to Failure', () { 122 | Result getNextInteger() => Failure(const MockError(451)); 123 | Result getNextAfterInteger(int n) => 124 | Failure(const MockError(404)); 125 | 126 | final nextIntegerUnboxedResults = 127 | getNextInteger().flatMap(getNextAfterInteger); 128 | 129 | expect( 130 | nextIntegerUnboxedResults, 131 | const TypeMatcher>(), 132 | ); 133 | }); 134 | 135 | test('Apply flatMapError transformation to failure operation results', () { 136 | Result getNextInteger() => Failure(const MockError(451)); 137 | Result getNextAfterInteger(MockError error) => 138 | Failure(MockError(error.code)); 139 | 140 | final nextIntegerUnboxedResults = 141 | getNextInteger().flatMapError(getNextAfterInteger); 142 | 143 | expect( 144 | nextIntegerUnboxedResults, 145 | const TypeMatcher>(), 146 | ); 147 | }); 148 | 149 | test( 150 | '''flatMapError does not apply transformation to success operation results''', 151 | () { 152 | Result getNextInteger() => Success(random!.nextInt(4)); 153 | Result getNextAfterInteger(MockError error) => 154 | Failure(MockError(error.code)); 155 | 156 | final nextIntegerUnboxedResults = 157 | getNextInteger().flatMapError(getNextAfterInteger); 158 | 159 | expect( 160 | nextIntegerUnboxedResults, 161 | const TypeMatcher>(), 162 | ); 163 | }); 164 | }); 165 | } 166 | 167 | Result getUser({required bool value}) => 168 | value ? Success('John Doe') : Failure(const MockError(404)); 169 | -------------------------------------------------------------------------------- /test/success_test.dart: -------------------------------------------------------------------------------- 1 | import 'package:result_type/src/success.dart'; 2 | import 'package:test/test.dart'; 3 | 4 | import 'utils/mock_error.dart'; 5 | 6 | void main() { 7 | group('Success', () { 8 | test('Should have a value 0', () { 9 | final success = Success(0); 10 | expect(success.value, 0); 11 | }); 12 | 13 | test('Two identical Successes should be equal', () { 14 | final success1 = Success(0); 15 | final success2 = Success(0); 16 | 17 | expect(success1, success2); 18 | }); 19 | 20 | test('Two identical Successes should have the same hashCode', () { 21 | final success1 = Success(0); 22 | final success2 = Success(0); 23 | 24 | expect(success1.hashCode, success2.hashCode); 25 | }); 26 | 27 | test('Can print to string', () { 28 | final success = Success(0); 29 | expect(success.toString(), 'Success: 0'); 30 | }); 31 | }); 32 | } 33 | -------------------------------------------------------------------------------- /test/test_all.dart: -------------------------------------------------------------------------------- 1 | import 'package:test/test.dart'; 2 | 3 | import 'failure_test.dart' as failure; 4 | import 'result_test.dart' as result; 5 | import 'success_test.dart' as success; 6 | 7 | void main() { 8 | group('success', success.main); 9 | group('failure', failure.main); 10 | group('result', result.main); 11 | } 12 | -------------------------------------------------------------------------------- /test/utils/mock_error.dart: -------------------------------------------------------------------------------- 1 | class MockError implements Exception { 2 | final int code; 3 | 4 | const MockError(this.code); 5 | 6 | @override 7 | String toString() => 'MockError(code: $code)'; 8 | } 9 | --------------------------------------------------------------------------------