异步 forEach AngularJS 后的回调 [英] callback after async forEach AngularJS

问题描述

如何在异步 forEach 循环后添加回调函数?

How do I add a callback function after an async forEach Loop?

这里有一些更好的上下文:

$scope.getAlbums = function(user, callback) {
    $scope.albumsList.forEach(function (obj, i) {
        $scope.getAlbum(user, obj.id, function(value){
            $scope.albums.push(value);
        });
    });
    // callback(); ???
};

$scope.getAlbums('guy123', function(){
    // forEach loop is all done!
    console.log($scope.albums)
});

控制器:

.controller('Filters', ['$scope','Imgur', function($scope, Imgur) {

    $scope.getAlbum = function(user, id, callback) {
        Imgur.album.get({user:user, id:id},    
            function(value) {
                return callback(value.data);
            }
        );
    }

    $scope.getAlbums = function(user, callback) {
        // Callback function at end of this forEach loop?
        // Request is async...
        $scope.albumsList.forEach(function (obj, i) {
            $scope.getAlbum(user, obj.id, function(value){
                $scope.albums.push(value);
            });
        });
    };
)]};

服务:

.factory('Imgur', function($resource) {
    return {
        album : $resource('https://api.imgur.com/3/account/:user/album/:id')
    }
});

推荐答案

正如 Andrew 所说，$q 和延迟对象的用法应该可以让您实现目标.

As Andrew said usage of $q and the deferred object should allow you to accomplish your goal.

你想使用 $q.all() 这将确保你所有的 promise 对象都被解析，然后你可以在 .then()

You want to use $q.all() This will make sure all of your promise objects are resolved and then you can call your call back in .then()

function MyCtrl($scope, $q, $http) {

    $scope.albumsList = [{
            id: 1,
            name: "11"
        }, {
            id: 2,
            name: "22"
        }
    ];
    $scope.albums = [];
    $scope.getAlbum = function(user, id, callback) {
        return $http.get("https://api.imgur.com/3/account/" + user + "/album/" + id).success(
            function(value) {
                return callback(value.data);
            }
        );
    }
    $scope.getAlbums = function (user, callback) {
        var prom = [];
        $scope.albumsList.forEach(function (obj, i) {
            prom.push($scope.getAlbum(user, obj.id, function(value){
                $scope.albums.push(value);
            }));
        });
        $q.all(prom).then(function () {
            callback();
        });
    };
    $scope.getAlbums('guy123', function () {
        alert($scope.albums.length);
    });
}

jsfiddle 上的示例

有效但不适用于 $http 调用

Works but not with $http calls

使用延迟对象，您可以访问一个承诺，您可以在其中更改连续的 then() 调用.当您解析延迟对象时，它将执行 foreach，然后执行您提供的回调函数.我试图进一步简化您的示例，以便它可以在 jsfiddle 中使用.

With the deferred object you gain access to a promise where you can change successive then() calls together. When you resolve the deferred object it will execute the foreach and then execute your call back function you supplied. I tried to simplify your example a bit further so it would work in jsfiddle.

function MyCtrl($scope, $http, $q) {

    $scope.albumsList = [{
        id: 1,
        name: "11"
    }, {
        id: 2,
        name: "22"
    }];
    $scope.albums = [];
    $scope.getAlbums = function (user, callback) {
        var deferred = $q.defer();
        var promise = deferred.promise;
        promise.then(function () {
            $scope.albumsList.forEach(function (obj, i) {
                $scope.albums.push(obj);
            });
        }).then(function () {
            callback();
        });
        deferred.resolve();
    };
    $scope.getAlbums('guy123', function () {
        alert($scope.albums.length);
    });
}

jsfiddle 示例

更多阅读延期和承诺.

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