Question

如何在async forEach循环后添加回调函数？

以下是一些更好的背景信息：

$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')
    }
});

Answer 1

正如安德鲁所说，使用$q和延迟对象可以让你实现目标。

您想使用$q.all()这将确保您的所有承诺对象都已解决，然后您可以在.then()

中回拨您的电话

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);
    });
}

<强> Example with this on jsfiddle

但$http次来电

无效

使用延迟对象，您可以访问承诺，您可以在其中一起更改连续的then()个呼叫。解析延迟对象时，它将执行foreach，然后执行您提供的回调函数。我试图进一步简化你的例子，以便在jsfiddle中工作。

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);
    });
}

<强> Example on jsfiddle

<强> A bit more reading on deferred and promises.

Answer 2

$scope.getAlbums = function(user, callback) {

        var promiseArr = [];
        $scope.albumsList.forEach(function (obj, i) {
            var anHttpPromise = 
            $scope.getAlbum(user, obj.id, function(value){
                $scope.albums.push(value);
            });
            promiseArr.push(anHttpPromise);
        });

        $q.all(promiseArr).then(function(){
            // This callback function will be called when all the promises are resolved.    (when all the albums are retrived)      
        })
    };

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

在上面的代码中：

使getAlbum返回承诺。
收集getAlbums列表
收集完所有承诺后，将传递promise数组 $q.all
$q.all方法返回一个回调的最终承诺一旦数组中的所有promise都被触发，函数将被触发解决。

Answer 3

使用针对1.1.3设定的$resource承诺PR commit，我能够使用$ q包装$resource次调用并控制其异步行为的流程。

$scope.getAlbum = function(user, id, callback) {
    var promise = Imgur.album.get({user:user, id:id}).$promise.then(
        function( value ){
            return callback(value.data);
        },
        function( error ){
            //Something went wrong!
        }
    )
    return promise;
}

$scope.getAlbums = function(user, callback) {
    var prom = [];
    $scope.albumsList.forEach(function (obj, i) {
        var promise =
        $scope.getAlbum(user, obj.id, function(value){
            $scope.albums.push(value);
        });
        prom.push(promise);

    });

    $q.all(prom).then(function () {
        callback();
    });
};

$scope.getAlbums(user, function(){
    // Totally works, bro.
    console.log($scope.albums);
});

Answer 4

看起来像延迟http://docs.angularjs.org/api/ng.$q，特别是链接承诺在这里很有用。

async forEach AngularJS之后的回调

4 个答案: