我已经在angularjs中实现了$ q.all,但是我无法使代码正常工作。这是我的代码:
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.promise);
}
return $q.all(promises);
}
这是我的 Controller ,它调用服务:
uploadService.uploadQuestion(questions).then(function(datas){
//the datas can not be retrieved although the server has responded
},
function(errors){
//errors can not be retrieved also
})
我认为在我的服务中设置$ q.all存在一些问题。
最佳答案
在javascript中,没有 block-level scopes
仅 function-level scopes
:
阅读有关javaScript Scoping and Hoisting的文章。
看看我如何调试您的代码:
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);
})
var deferred= $q.defer();
时,它的提升了到函数的顶部,这意味着javascript在for loop
之外的函数范围内声明了此变量。 closure scope
中。 用
angular.forEach
解决方案:这是一个演示插件: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);
}
我最喜欢的方法是使用
Array#map
:这是一个演示插件: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);
}