javascript - 链接通过 for 循环创建的多个 Promise

Question

我一直在通过 this link 研究 Promise我明白了它的想法

var parentID;

$http.get('/api/user/name')
  .then(function(response) {

  parentID = response.data['ID'];
  for (var i = 0; i < response.data['event-types'].length; i++) {
    return $http.get('/api/security/' + response.data['event-types'][i]['key']);
  }

  })
  .then(function(response) {

    // response only returns one result of the many promises from the for loop
    // do something with parentID; 

  });

但是，我的用例需要循环并发送创建多个 promise 。我尝试链接上面的示例，但只有从 for 循环创建的唯一一个 promise 被执行。

如何在继续访问变量parentID的同时继续链接所有 promise ？

Answer 1

您应该使用$q.all，因为它与 AngularJS 摘要周期集成。

var parentID;

$http.get('/api/user/name')
  .then(function(response) {

      parentID = response.data['ID'];
      var promiseList = [];
      for (var i = 0; i < response.data['event-types'].length; i++) {
          var iPromise = $http.get('/api/security/' + response.data['event-types'][i]['key']);
          promiseList.push(iPromise);
      };
      return $q.all(promiseList);

  })
  .then(function(responseList) {

       console.log(responseList);

  });

来自文档:

all(promises);

Combines multiple promises into a single promise that is resolved when all of the input promises are resolved.

Parameters

An array or hash of promises.

Returns

Returns a single promise that will be resolved with an array/hash of values, each value corresponding to the promise at the same index/key in the promises array/hash. If any of the promises is resolved with a rejection, this resulting promise will be rejected with the same rejection value.

--AngularJS $q Service API Reference -- $q.all