Flutter 卡住，使用联合/密封类时如何返回值并停止执行函数

Question

我有这个方法，我使用卡住的 flutter 包来处理网络状态。

我想停止异步方法的执行，以防我使用联合/密封类收到失败响应。

 void wantedToStopExecutionInAsync() async {
    var resultFromNetworkCall = await myNetworkCall();

    resultFromNetworkCall.when(
      success: (value) {
        //do some work;
      },
      failure: (exception) {
        print(exeption);
        //Here I want to stop the execution of async function wantedToStopExecutionInAsync()
        return;
      }
    );

    //If result is a failure, I dont want to process the next line of code
    someOtherWork();
  }

我想在收到失败响应时停止执行，这可能吗？

一个选项是

 void wantedToStopExecutionInAsync() async {
    var resultFromNetworkCall = await myNetworkCall();

    resultFromNetworkCall.when(
      success: (value) {
        //do some work;
      },
      failure: (exception) {
        print(exeption);
        //Here I want to stop the execution of async function wantedToStopExecutionInAsync()
        return;
      }
    );

    if (resultFromNetworkCall is Failure) {
        return;
    }

    //If result is a failure, I dont want to process the next line of code
    someOtherWork();
  }

但这并不好。有什么建议吗？

Answer 1

没那么难。在联合中返回一个 bool 结果。检查下一个代码片段:

void wantedToStopExecutionInAsync() async {
  var resultFromNetworkCall = await myNetworkCall();

  bool success = resultFromNetworkCall.when(
    success: (value) {
      return true;
    },
    failure: (exception) {
      print(exeption);
      return false; // NOTE: Return of false
    },
  );
  
  //Stop the execution of async function wantedToStopExecutionInAsync()
  if (success == false || resultFromNetworkCall is Failure) {
    return;
  }

  //If result is a failure, I dont want to process the next line of code
  someOtherWork();
}