如何访问promise` .then`方法之外的变量？ [英] How can I access a variable outside a promise `.then` method?

问题描述

我正在开发Spotify应用。我能够登录并获取我的令牌。我的问题是我无法访问方法之外的变量。在这种情况下getCurrentUser

I'm working on a Spotify app. I'm able to login and get my token. My problem is I cannot access a variable outside the method. In this case "getCurrentUser"

这是我的方法：

function getUser() {
  if ($localStorage.token == undefined) {
    throw alert("Not logged in");
  } else {
    Spotify.getCurrentUser().then(function(data) {
      var names = JSON.stringify(data.data.display_name);
      console.log(names)
    })
  }
};

正如您所见，我在控制台上记录了该名称，并且我在控制台中获得了正确的值。但是只有在我调用函数 getUser（）时才能在那里工作，即使返回names变量，我也得到 undefined 。

As you can see I console.logged the name and I do get the right value in the console. But only works there if I call the function getUser() I get undefined even with a return of the names variable.

我需要 $ scope 该变量。

推荐答案

getUser（）没有返回任何内容。您需要从 Spotify.getCurrentUser（）返回承诺，然后在中返回名称 它由外部函数返回。

getUser() is not returning anything. You need to return the promise from the Spotify.getCurrentUser(), and then when you return names within that it is returned by the outer function.

function getUser() {

    if ( $localStorage.token == undefined) {
        throw alert("Not logged in");
    }
    else {
        return Spotify.getCurrentUser().then(function(data) {
            var names = JSON.stringify(data.data.display_name);
            console.log(names)
            return names;
        })
    }
}

上面回答了为什么你在调用 getUser（）时得到 undefined 的原因，但是如果你想使用最终结果你也想改变你从getUser获得的值的方式 - 它返回一个promise对象，而不是你所追求的最终结果，所以你的代码想要调用promise的<承诺得到解决时code>然后方法：

The above answered why you were getting undefined when calling getUser(), but if you want to work with the end result you also want to change how you're using the value you get from getUser - it returns a promise object, not the end result you're after, so your code wants to call the promise's then method when the promise gets resolved:

getUser()                        // this returns a promise...
   .then(function(names) {       // `names` is the value resolved by the promise...
      $scope.names = names;      // and you can now add it to your $scope
   });

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