angularJS中的同步http调用 [英] synchronous http call in angularJS

问题描述

我有以下情况，我需要来自特定网址的数据。我写了一个带参数'url'的函数。在函数内部，我有$ http.get方法，它调用url。数据将返回到调用函数

I have the following scenario, I need data from a particular url. I have written a function which takes parameter 'url'. Inside the function I have the $http.get method which makes a call to the url. The data is to be returned to the calling function

var getData = function (url) {
    var data = "";

    $http.get(url)
        .success( function(response, status, headers, config) {
             data = response;
        })
        .error(function(errResp) {
             console.log("error fetching url");
        });
    return data;
}

问题如下，$ http.get是异步的，在响应之前获取后，函数返回。因此，调用函数将数据作为空字符串获取。在从网址中提取数据之前，如何强制该函数不返回？

The problem is as follows, $http.get is asynchronous, before the response is fetched, the function returns. Therefore the calling function gets the data as empty string. How do I force the function not to return until the data has been fetched from the url?

推荐答案

看看承诺克服这些问题，因为它们在角落世界中被广泛使用。

Take a look at promises to overcome such issues, because they are used all over the place, in angular world.

你需要使用 $ q

var getData = function (url) {
    var data = "";
    var deferred = $q.defer();

    $http.get(url)
        .success( function(response, status, headers, config) {
             deferred.resolve(response);
        })
        .error(function(errResp) {
             deferred.reject({ message: "Really bad" });
        });
    return deferred.promise;
}

这是关于 promises and $ q

更新：

FYI， $ http 服务本身返回一个承诺，所以 $ q 在这种情况下不一定是必需的（因此反模式。

FYI, $http service itself returns a promise, so $q is not necessarily required in this scenario(and hence an anti-pattern).

但是不要让这个成为跳过阅读关于$ q和承诺的理由。

But do not let this be the reason to skip reading about $q and promises.

所以上面的代码相当于以下内容：

So the above code is equivalent to following:

var getData = function (url) {
    var data = "";
    return $http.get(url);
}

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