Angularjs $q.all Angularjs $q.all angularjs angularjs

Angularjs $q.all


In javascript there are no block-level scopes only function-level scopes:

Read this article about javaScript Scoping and Hoisting.

See how I debugged your code:

var deferred = $q.defer();deferred.count = i;console.log(deferred.count); // 0,1,2,3,4,5 --< all deferred objects// some code.success(function(data){   console.log(deferred.count); // 5,5,5,5,5,5 --< only the last deferred object   deferred.resolve(data);})
  • When you write var deferred= $q.defer(); inside a for loop it's hoisted to the top of the function, it means that javascript declares this variable on the function scope outside of the for loop.
  • With each loop, the last deferred is overriding the previous one, there is no block-level scope to save a reference to that object.
  • When asynchronous callbacks (success / error) are invoked, they reference only the last deferred object and only it gets resolved, so $q.all is never resolved because it still waits for other deferred objects.
  • What you need is to create an anonymous function for each item you iterate.
  • Since functions do have scopes, the reference to the deferred objects are preserved in a closure scope even after functions are executed.
  • As #dfsq commented: There is no need to manually construct a new deferred object since $http itself returns a promise.

Solution with angular.forEach:

Here is a demo plunker: http://plnkr.co/edit/NGMp4ycmaCqVOmgohN53?p=preview

UploadService.uploadQuestion = function(questions){    var promises = [];    angular.forEach(questions , function(question) {        var promise = $http({            url   : 'upload/question',            method: 'POST',            data  : question        });        promises.push(promise);    });    return $q.all(promises);}

My favorite way is to use Array#map:

Here is a demo plunker: http://plnkr.co/edit/KYeTWUyxJR4mlU77svw9?p=preview

UploadService.uploadQuestion = function(questions){    var promises = questions.map(function(question) {        return $http({            url   : 'upload/question',            method: 'POST',            data  : question        });    });    return $q.all(promises);}


$http is a promise too, you can make it simpler:

return $q.all(tasks.map(function(d){        return $http.post('upload/tasks',d).then(someProcessCallback, onErrorCallback);    }));


The issue seems to be that you are adding the deffered.promise when deffered is itself the promise you should be adding:

Try changing to promises.push(deffered); so you don't add the unwrapped promise to the array.

 UploadService.uploadQuestion = function(questions){            var promises = [];            for(var i = 0 ; i < questions.length ; i++){                var deffered  = $q.defer();                var question  = questions[i];                 $http({                    url   : 'upload/question',                    method: 'POST',                    data  : question                }).                success(function(data){                    deffered.resolve(data);                }).                error(function(error){                    deffered.reject();                });                promises.push(deffered);            }            return $q.all(promises);        }