如何返回后单诺循环（产生在每个迭代上的承诺）是完整的？ [英] How to return single promise after for loop (which produces a promise on every iteration) is complete?

问题描述

我有我的承诺回报code的一个问题，我有一个函数 getTagQuotes 其中包含一个for循环，可以使多个调用的API返回的数据为阵列

I have a problem with my promise return code, I have a function getTagQuotes which contains a for loop which can make multiple calls an API to return data into an array.

我如何code这个开头如下：

How my code for this begins below:

// If there are tags, then wait for promise here:
if (tags.length > 0) {

    // Setting promise var to getTagQuotes:
    var promise = getTagQuotes(tags).then(function() {
        console.log('promise =',promise);

        // This array should contain 1-3 tags:
        console.log('tweetArrayObjsContainer =',tweetArrayObjsContainer);

        // Loop through to push array objects into chartObj:
        for (var i=0; i<tweetArrayObjsContainer.length; i++) {
            chartObj.chartData.push(tweetArrayObjsContainer[i]);
        }

        // Finally draw the chart:
        chartDirective = ScopeFactory.getScope('chart');
        chartDirective.nvd3.drawChart(chartObj.chartData);
    });
}

我getTagQuotes与承诺返回功能：

My getTagQuotes function with the promise return:

function getTagQuotes(tags) {
    var deferred = $q.defer(); // setting the defer
    var url      = 'app/api/social/twitter/volume/';

    // My for loop, which only returns ONCE, even if there are 3 tags
    for (var i=0; i<tags.length; i++) {
        var loopStep = i;
        rawTagData   = [];

        // The return statement
        return GetTweetVolFactory.returnTweetVol(url+tags[i].term_id)
            .success(function(data, status, headers, config) {
                rawTagData.push(data);

                // One the last loop, call formatTagData
                // which fills the tweetArrayObjsContainer Array
                if (loopStep === (rawTagData.length - 1)) {
                    formatTagData(rawTagData);
                    deferred.resolve();
                    return deferred.promise;
                }
            });
    }

    function formatTagData(rawData) {

        for (var i=0; i<rawData.length; i++) {
            var data_array = [];
            var loopNum = i;

            for (var j=0; j<rawData[loopNum].frequency_counts.length; j++) {
                var data_obj = {};
                data_obj.x = rawData[loopNum].frequency_counts[j].start_epoch;
                data_obj.y = rawData[loopNum].frequency_counts[j].tweets;
                data_array.push(data_obj);
            }

            var tweetArrayObj = {
                "key" : "Quantity"+(loopNum+1), "type" : "area", "yAxis" : 1, "values" : data_array
            };

            tweetArrayObjsContainer.push(tweetArrayObj);
        }
    }
}

这行采取通知

return GetTweetVolFactory.returnTweetVol(url+tags[i].term_id)

这是我的内循环：

it's inside my for loop:

for (var i=0; i<tags.length; i++)

一切都很正常，如果我只能通过一次有循环。但是只要有另一个标签（最多3个），它仍然只返回第一个循环/数据。它不会等到循环已经完成。然后返回的承诺。所以，我的 tweetArrayObjsContainer 总是只有第一个标记。

推荐答案

三个问题：

1. 您没有回从 getTagQuotes 方法递延承诺。


2. 您在看 I 来看看，如果你是通过循环和for循环已经完成（我==（标签。长度 - 1））之前的第一个成功甚至被称为
。

3. 您叫收益在循环的第一次迭代，让你甚至没有得到第二个项目。

1. you didn't return the deferred promise from the getTagQuotes method.
2. you were looking at i to see if you were through the loop, and the for loop is already completed (i == (tags.length - 1)) before the first success is even called.
3. you called return in the first iteration of the loop so that you didn't even get to the 2nd item.

下面是纠正code（没有测试它尚未）

Here's corrected code (didn't test it yet)

function getTagQuotes(tags) {
    var deferred = $q.defer(); // setting the defer
    var url      = 'app/api/social/twitter/volume/';
    var tagsComplete = 0;

    for (var i=0; i<tags.length; i++) {
        rawTagData   = [];
        GetTweetVolFactory.returnTweetVol(url+tags[i].term_id)
            .success(function(data, status, headers, config) {
                rawTagData.push(data);
                tagsComplete++;

                if (tagsComplete === tags.length) {
                    formatTagData(rawTagData);
                    deferred.resolve();
                }
            });
    }

    return deferred.promise;
}

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