我们如何从未来的方法中获得价值? [英] How can we get value from future method in flutter?

问题描述

我有此函数返回存储在其中的"SharedPreference"值.

I have this function returning the "SharedPreference" value stored in it.

  Future<bool> getLoginStatus() async {
    final prefs = await SharedPreferences.getInstance();
    final loggedInStatus = prefs.getBool("loggedInStatus");

    if (loggedInStatus == null) {
      return false;
    }
    return loggedInStatus;
  }

上面的函数在名为"Constants.dart"的类中.当我通过在不同类中进行简单打印来进行从"getLoginStatus()"函数中提取值的测试时.

Above function is in the class named "Constants.dart". When I do the test of extracting value from "getLoginStatus()" function by simple printing in different class.

 print("Login status : " + Constants().getLoginStatus().toString());

下面给出了我的输出.为什么是未来实例"?为什么不简单地选择对还是错呢?

It give me below as an output. Why "Instance of 'Future'"? Why not simple either true or false?

I/flutter (19683): Login status : Instance of 'Future<bool>'

推荐答案

由于您的getLoginStatus()是异步的，因此将来会返回布尔值.因此，要获取该值，您必须等待过程将其返回.

Since your getLoginStatus() is asynchronous and it return a bool value in future. So to get the value you have to await for the process to return it.

因此检索该值的正确代码将是:

So the correct Code to retrieve the value would be :

bool loggedInStatus = await Constants().getLoginStatus();
print(loggedInStatus);

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