如何从Dart（Dartz）中的任一类型轻松提取Left或Right

一尘不染

如何从Dart（Dartz）中的任一类型轻松提取Left或Right

flutter

我希望从返回类型的方法中轻松提取值Either<Exception, Object>。

我正在做一些测试，但是无法轻松测试我的方法的返回。

例如：

final Either<ServerException, TokenModel> result = await repository.getToken(...);

为了测试我能够做到这一点

expect(result, equals(Right(tokenModelExpected))); // => OK

现在如何直接检索结果？

final TokenModel modelRetrieved = Left(result); ==> Not working..

我发现我必须像这样进行投射：

final TokenModel modelRetrieved = (result as Left).value; ==> But I have some linter complain, that telling me that I shouldn't do as to cast on object...

我也想测试该异常，但是它不起作用，例如：

expect(result, equals(Left(ServerException()))); // => KO

所以我尝试了这个

expect(Left(ServerException()), equals(Left(ServerException()))); // => KO as well, because it says that the instances are different.

阅读 515

2020-08-13

共1个答案

一尘不染

好的，这里是我的问题的解决方案：

提取/检索数据

final Either<ServerException, TokenModel> result = await repository.getToken(...);
result.fold(
 (exception) => DoWhatYouWantWithException, 
 (tokenModel) => DoWhatYouWantWithModel
);

//Other way to 'extract' the data
if (result.isRight()) {
  final TokenModel tokenModel = result.getOrElse(null);
}

测试异常

//You can extract it from below, or test it directly with the type
expect(() => result, throwsA(isInstanceOf<ServerException>()));

2020-08-13