如何在 promise `.then` 方法之外访问变量? [英] How can I access a variable outside a promise `.then` method?

问题描述

我正在开发 Spotify 应用.我可以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)
    })
  }
};

如您所见，我在控制台中记录了名称，并且确实在控制台中获得了正确的值.但只有在我调用函数 getUser() 时才在那里工作，即使返回了 names 变量，我也会得到 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那个变量.

推荐答案

getUser() 没有返回任何内容.您需要从 Spotify.getCurrentUser() 返回承诺，然后当您在 that 内返回 names 时，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;
        })
    }
}

上面回答了为什么您在调用 getUser() 时得到 undefined，但如果您想使用最终结果，您还想改变您的方式使用您从 getUser 获得的值 - 它返回一个承诺对象，而不是您所追求的最终结果，因此您的代码希望在承诺得到解决时调用承诺的 then 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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