避免多次Ajax请求angularJS [英] Avoid multiple ajax requests angularJS

问题描述

我试图避免多次Ajax请求在工厂的服务器。我已经添加了一个小的缓存服务，但它是不够的，我的目标是：在服务器响应之前，这个工厂可以被称为多次，造成多次请求到服务器的产生。

要避免这一点，我添加了第二个承诺对象，如果AJAX请求已经被执行，对象是尚未在缓存中，比它应该等待第二承诺解决，但看起来像我失去了一些东西。

这是我的code：

  myApp.factory（'用户'，['Restangular'，'$ Q'，
  功能（Restangular，$ Q）{
    VAR userCache，alreadyRun = FALSE;
    返回{
      的getUser：功能（）{
        变种推迟= $ q.defer（），firstRun = $ q.defer（）;        如果（userCache＆安培;！＆安培;！alreadyRun）{
          alreadyRun = TRUE;          Restangular.all（用户）的GetList（）。然后（功能（用户）{
            的console.log（'获取用户现场）;
            userCache =用户[0] .email;
            firstRun.resolve（用户[0] .email）;
          }）;
        }否则如果（userCache＆安培;！＆安培; alreadyRun）{
          的console.log（'等待第一个承诺要解决'）;
          firstRun.then（功能（用户）{
            的console.log（'解决的承诺'）;
            deferred.resolve（userCache）;
          }）;        }其他{
          的console.log（'解决从缓存中的承诺'）;
          deferred.resolve（userCache）
        }
        返回deferred.promise;
      }
    };
  }
]）;
 

解决方案

您可以只归还当初的诺言，如果请求已经作出。像这样的东西应该工作;

  myApp.factory（'用户'，['Restangular'，'$ Q'，
  功能（Restangular，$ Q）{
    VAR递延= FALSE;    返回{
      的getUser：功能（）{        如果（延期）{
          返回deferred.promise;
        }        递延= $ q.defer（）;        Restangular.all（用户）的GetList（）。然后（功能（用户）{
          deferred.resolve（用户[0] .email）;
        }）;        返回deferred.promise;
      }
    };
  }
]）;
 

也有看 Restangular文档

I am trying to avoid multiple ajax requests to the server in a factory. I already added a small caching service, but it is not enough for what I aim: this factory can be called several times before the server responds, causing the generation of multiple requests to the server.

To avoid this I added a second promise object, which if the AJAX request have been performed and the object is not yet in cache, than it should wait for a second promise to be resolved, but looks like I am missing something.

This is my code:

myApp.factory('User', ['Restangular', '$q',
  function (Restangular, $q) {
    var userCache, alreadyRun = false;
    return {
      getUser: function () {
        var deferred = $q.defer(), firstRun= $q.defer();

        if (!userCache && !alreadyRun) {
          alreadyRun = true;

          Restangular.all('user').getList().then(function (user) {
            console.log('getting user live ');
            userCache = user[0].email;
            firstRun.resolve(user[0].email);
          });
        } else if (!userCache && alreadyRun) {
          console.log('waiting for the first promise to be resolved ');
          firstRun.then(function(user) {
            console.log('resolving the promise');
            deferred.resolve(userCache);
          });

        } else {
          console.log('resolving the promise from the cache');
          deferred.resolve(userCache)
        }
        return deferred.promise;
      }
    };
  }
]);

解决方案

You could just return the original promise if the request has already been made. Something like this should work;

myApp.factory('User', ['Restangular', '$q',
  function (Restangular, $q) {
    var deferred = false;

    return {
      getUser: function () {

        if(deferred) {
          return deferred.promise;
        }

        deferred = $q.defer();

        Restangular.all('user').getList().then(function (user) {
          deferred.resolve(user[0].email);
        });

        return deferred.promise;
      }
    };
  }
]);

Also have a look at the Restangular documentation for caching requests

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