How to multi-callback a promise in AngularJs with $q?

Question

I'm using the code below in order to simplify the backend requests but I didn't catch how to call either a success method or an error method.

How can I reach the expected behavior commented in the code?

 
app.factory('REST', function ($http, $q, sweetAlert) {

    return {
        load: function (module, action, data) {
            var deferred = $q.defer();
            var promise = deferred.promise;         
            $http
            .post('/api/'+module+'.php?action='+action, data)
            .success(function (data) {

                if(data.error)
                {
                    sweetAlert.swal({
                        title: "Error",
                        text: data.error,
                        type: "warning"
                    });
                //HERE I WANT TO CALL .error(details)
                }
                else
                    deferred.resolve(data.result);

                        }).error(function () {
                //HERE I WANT TO CALL .error(details)
            });

            promise.success = function(fn) {
                promise.then(fn);
                return promise;
            }

            return promise;
        }
    };
});

This is the code which uses the code above:

$scope.login = function () {
    $scope.loading = true;
    var payload = {'credentials': $scope.logindata};
    REST.load('access', 'login', payload).success(function(data) {
        if(data.redirect)
            $state.go(data.redirect);
        $scope.loading = false;
    }).error(function(data) { //THIS SHOULD BE CALLED
        $scope.loading = false;
    });
}

Answer 1

First of all, I strongly discourage you from attaching .success to the promise you are returning. This is not Promises/A-compliant, and its subtle difference from .then (as is implemented by $http) causes a lot of confusion. Just return a pure promise.

Other than that, a few things to note:

1) you don't need another $q.defer and deferred.resolve() - just chain to the original promise of $http and return the resulting promise. (see deferred anti-pattern)

2) to reject a promise - that is, to cause the .catch (not .error - see above about the subtle difference) to fire - you should return $q.reject().

All of the above produces the following:

app.factory('REST', function($http, $q, sweetAlert){
  return {
    load: function(module, action, data) {
      // this "return" returns the promise of $http.then
      return $http.post('/api/' + module + '.php?action=' + action, data)
        .then(function(response) {
          var data = response.data; // .then gets a response, unlike $http.success

          if (data.error) {
            sweetAlert.swal({
              title: "Error",
              text: data.error,
              type: "warning"
            });

            //HERE I WANT TO CALL .error(details)

            return $q.reject(data.error);
          }

          return data.result; // what you would have "resolved"
        });
    }
  };
})

Then, as I said above, use the .then/.catch as you would with promises:

$scope.login = function () {
    $scope.loading = true;
    var payload = {'credentials': $scope.logindata};
    REST.load('access', 'login', payload)
        .then(function(data) {
          if(data.redirect)
             $state.go(data.redirect);
          $scope.loading = false;
        })
        .catch(function(error) {
          $scope.loading = false;
        });
}

Answer 2

Update yr code as below

app.factory('REST', function ($http, $q, sweetAlert) {
   return {
       load: function (module, action, data) {
              var deferred = $q.defer();                  
                  $http.post('/api/'+module+'.php?action='+action, data)
                          .success(function (data) {
                              if(data.error)
                              {
                                  sweetAlert.swal({
                                      title: "Error",
                                      text: data.error,
                                      type: "warning"
                                  });     
                                 //HERE I WANT TO CALL .error(details)                                
                                 deferred.reject(data.error);
                              }
                              else{
                                deferred.resolve(data.result);
                              }

                         })
                         .error(function (error) {
                              //HERE I WANT TO CALL .error(details)
                              deferred.reject(error);   
                          });

               return defferred.promise;
          }
   };
});

for yr controller

 $scope.login = function () {
     $scope.loading = true;
     var payload = {'credentials': $scope.logindata};
     REST.load('access', 'login', payload).then(
       function(data) {
         if(data.redirect)
             $state.go(data.redirect);
             $scope.loading = false;
       },
       function(error) {
          $scope.loading = false;
       });
   }