文件列表:

.metadata (309, 2021-08-31)
CHANGELOG.md (1241, 2021-08-31)
LICENSE (1076, 2021-08-31)
example/ (0, 2021-08-31)
example/lib/ (0, 2021-08-31)
example/lib/either_option_example.dart (1045, 2021-08-31)
example/lib/model/ (0, 2021-08-31)
example/lib/model/server_error.dart (135, 2021-08-31)
example/lib/model/user.dart (385, 2021-08-31)
example/lib/repository_example.dart (1125, 2021-08-31)
example/pubspec.yaml (342, 2021-08-31)
lib/ (0, 2021-08-31)
lib/either_option.dart (76, 2021-08-31)
lib/src/ (0, 2021-08-31)
lib/src/either.dart (3010, 2021-08-31)
lib/src/option.dart (3143, 2021-08-31)
pubspec.yaml (420, 2021-08-31)
test/ (0, 2021-08-31)
test/either_test.dart (1743, 2021-08-31)
test/option_test.dart (2738, 2021-08-31)

# either_option __either_option__ is a simple library typed for easy and safe error handling with functional programming style in Dart. It aims to allow flutter/dart developpers to use the 2 most popular patterns and abstractions : `Either` and `Option`, mainly used in FP language like Scala, Haskell, OCaml,... # Installation Prerelease versions that support null safety Package link on pub [either_option](https://pub.dev/packages/either_option) In your pubspec.yaml dependencies add either_option: ^2.0.0 # Overview ## Either `Either` Represents a value of one of two possible types. By convention we put missing or error value in an instance of `Left` and expected success value in an instance of `Right`. For example, we fetch an url from a repository [repository](example/lib/repository_example.dart) to get an *User* details and use `Either` : ```dart Future> getUser(int id) async { final baseUrl = "https://fakerestapi.azurewebsites.net/api/Users/$id"; final res = await http.get(baseUrl); if (res.statusCode == 200) { dynamic body = json.decode(res.body); User user = User.fromJson(body); return Right(user); } if (res.statusCode == 404) return Left(ServerError("This user doesn't exist")); return Left(ServerError("Unknown server error")); } ``` So now to consume result we can use for example `fold` method and say what to do with value : ```dart main() async { final Repository repository = Repository(); final Either res = await repository.getUser(3); final defaultUser = User(id: 0, username: "ko", password: "ko"); final userName = res.fold((_) => defaultUser.username, (user) => user.username); print(userName); // "User 3" //if res was a Left, print(userName) would give "ko" } ``` ## Option `Option` Represents a value of one of two possible types. By convention we consider missing value as an instance of `None` and expected success value in an instance of `Some`. ```dart Future> getUserOpt(int id) async { final res = await http.get(baseUrl); return Option.cond( res.statusCode == 200, User.fromJson(json.decode(res.body))); } // ----------------------------------------- main() async { final Repository repository = Repository(); final Option res = await repository.getUserOpt(3); final defaultUser = User(id: 0, username: "ko", password: "ko"); final userName = res.getOrElse(defaultUser).username; print(userName); // "User 3" //if res was a None, print(userName) would give "ko" } ``` ## Ressources & explanation [Medium article](https://medium.com/@cb.yannick/a-small-monad-library-for-dart-flutter-project-e49b71205bd0?source=friends_link&sk=21c7527322b281aa6e161bad27086952) # Features Functions available : | | Option | Either| | ------------ |:---------:| -----:| | fold | :+1: | :+1: | | map | :+1: | :+1: | | flatMap | :+1: | :+1: | | getOrElse | :+1: | | | orElse | :+1: | | | toLeft | :+1: | | | toRight | :+1: | | | toEither | :+1: | | | Option.empty | :+1: | | | Option.of | :+1: | | | filter | :+1: | | | exists | :+1: | | | contains | :+1: | | | swap | | :+1:| | cond | :+1: | :+1:| # Example * [Either & Option](example/lib/either_option_example.dart) * [Repository](example/lib/repository_example.dart) # Tests * [Either](test/either_test.dart) * [Option](test/option_test.dart)

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