在初步承诺成功后拒绝内心承诺？ [英] Rejecting inner promise after initial promise has succeeded?

问题描述

我有一个函数在产生一些数据之前发出两个异步请求。

I have a function which issues two async requests before yielding some data.

该方法的调用者不需要知道其实现细节。所有来电者的需求是：

The caller of the method does not need to know about its implementation details. All the caller needs is:

• 第二次请求返回的数据。


• 能力调用abort而不是返回数据。

由于在第一个承诺完成后可以调用abort，这很复杂。第二个请求已在进行中，但调用者尚未接收数据。因此，调用者假设它可以调用abort，但是拒绝第一个promise将没有任何效果。

This is complicated by the fact that abort can be called after the first promise is done. The second request is already in-flight, but the caller has yet to receive data. So, the caller assumes it can call abort, but rejecting the first promise will have no effect.

我使用以下方法解决了这个问题，但感觉非常hacky。我错过了什么吗？

I work around this issue with the following, but it feels pretty hacky. Am I missing something?

var ajaxOptions = {
  url: 'https://www.googleapis.com/youtube/v3/search',
  data: {
    part: 'id',
    key: 'AIzaSyDBCJuq0aey3bL3K6C0l4mKzT_y8zy9Msw',
    q: 'Hello'
  }
};

function search(options) {
  var jqXHR = $.ajax(ajaxOptions);

  var innerJqXHR = null;
  jqXHR.then(function(data, statusText, jqXHR) {
    innerJqXHR = $.ajax(ajaxOptions);
    innerJqXHR.done(options.done);
    innerJqXHR.fail(options.fail);

    return innerJqXHR;
  }, options.fail);

  return {
    promise: jqXHR,
    innerPromise: innerJqXHR,
    fullAbort: function() {
      jqXHR.abort();

      if (innerJqXHR !== null) {
        innerJqXHR.abort();
      }
    }
  }
}

var searchReturn = search({
  done: function() {
    console.log('inner done');
  },
  fail: function() {
    console.log('inner or outer fail');
  }
});

searchReturn.fullAbort();

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

推荐答案

由于您的代码看起来有点像伪代码（对我来说是未解答的问题），我能提供的最好的是一个想法的框架。一般的想法是你从搜索函数中返回两个东西，一个只在解析了两个ajax调用时解析的promise和一个可以调用以中止该过程的中止函数。

Since your code looks a little like pseudo-code (unanswered questions in it for me), the best I can offer is a framework of an idea. The general idea is that you return two things from your search function, a promise that is resolved only when both ajax calls are resolved and an abort function that can be called to abort the process.

function search(options) {
    var activeAjax = $.ajax(args for first ajax call).then(function(data) {
        // second ajax call changes activeAjax so abort will work
        // on the active ajax call
        activeAjax = $.ajax(args for second ajax call).then(function(data) {
            activeAjax = null;
            // collect your final data here and return it
            // this will be the resolved value of the final promise
            return finalData;
        });
        return activeAjax;
    });

    return {
        promise: activeAjax,
        abort: function() {
            if (activeAjax) {
                activeAjax.abort();
            }
        }
    };
}

// usage:
var searchInProgress = search(...);
searchInProgress.promise.then(function(data) {
    // search finished successfully, answer is in data
}, function(err) {
    // either one of the promises failed
});

// and, at any time, you can call searchInProgress.abort();

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