javascript – $q.defer()不使用Angular服务

我是angular的$q的新手,我正在尝试构建一个API调用服务并将其返回给控制器.

问题：无论我如何格式化它,服务都会在它到达$http.get(…)之前返回

服务：

   // methods: query new, get existing
  makeRequest: function(url, following) {
      // create promise
      var deferred = $q.defer();

      $http.get(url, {
          params: {
              "following": JSON.stringify(following)
          }
      })
          .then(function(res) {

              console.log(res);
              deferred.resolve(res.data);
          });

      return deferred.promise;
  },

  getFeed: function(user) {
      console.log('>> userService[getUser]: retrieving user...');


      if (!this.activities) {
          // Request has not been made, setting user profile. 
          console.log('>> userService[getUser]: No user stored, making request...');
          var following = this.compileArray(user);
          console.log(following);
          this.activities = this.makeRequest('api/network/activities', following);
      };

      // Return the myObject stored on the service
      return this.activities;
  }

调节器

$scope.recentActivity = activityService.getFeed(profile);

// also tried
activityService.getFeed(profile).then(function (res) {
                  $scope.recentActivity = res;
                  console.log(res);
                }); 

编辑：上午9:40 05/06/2015

如果可能的话,我想从服务中检索控制器中的活动列表,就像它是新的一样(使用.then).那是可能/不好的做法吗？

  getFeed: function(user) {
    if (!this.activities) { 
      ...
    } else {
      feedPromise = $q(function(resolve){ resolve(this.activities) });
      console.log(feedPromise);
      // returns: {$$state: Object, then: function, catch: function, finally: function}

      feedPromise.then(function(res) {
        console.log(res);
        // returns: undefined
      });

      console.log(that.activities);
      // Works, returns list of activities. 

   }

解决方法:

除非您将带有回调的基于非承诺的API转换为基于承诺的API,否则无需使用$q.defer(即使这样,建议使用$q(函数(解析,拒绝){. ..})).

$http已经返回一个承诺 – 只返回那个(或链接的.then承诺);

var httpResponsePromise = $http.get(url); // returns a promise
var actualDataPromise = httpResponsePromise.then(function(resp){ return resp.data; });

return actualDataPromise;

或更短(和典型)：

return $http.get(url).then(function(response){ 
   return response.data;
});

其次,承诺返回API会立即同步返回承诺 – 而不是结果.你需要一个.then才能得到结果.

最后,一旦API是异步的,它应始终是异步的 – 不要将其转换为同步或有时同步API.因此,无论在哪里,一直到数据的最终接收者,您都需要使用.then处理程序.

因此,您的服务API可以非常简单：

makeRequest: function(url, following){
   return $http.get(url, {params: { "following": following }})
             .then(function(response){
                return response.data;
             });
},

getFeed: function(user) {
   var that = this;

   var feedPromise;

   if (!that.activities) {
      var following = this.compileArray(user);

      feedPromise = this.makeRequest('api/network/activities', following)
          .then(function(activities){
             that.activities = activities;
             return activities;
          });
   } else {
      feedPromise = $q(function(resolve){ resolve(that.activities); });
      // or you could have cached the old feedPromise and returned that
   }

   return feedPromise;
}

控制器中的用法与任何其他基于promise的API一样：

activityService.getFeed(profile)
   .then(function(activities) {
      $scope.recentActivity = activities;
   }); 

标签：javascript,angularjs,q
来源： https://codeday.me/bug/20190623/1274401.html