避免多个ajax请求angularJS

Question

我试图避免在工厂中向服务器发出多个ajax请求.我已经添加了一个小的缓存服务,但这还不足以满足我的目标:在服务器响应之前可以多次调用此工厂,从而导致向服务器生成多个请求.

为了避免这种情况,我添加了第二个promise对象,如果已经执行了AJAX请求并且对象尚未在缓存中,那么它应该等待第二个promise被解析,但看起来我错过了一些东西.

这是我的代码:

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;
      }
    };
  }
]);

Answer 1

如果已经提出请求,您可以返回原始承诺.这样的事情应该有效;

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;
      }
    };
  }
]);

另请参阅Restangular文档以获取缓存请求