无法使用 $http angularjs 获取结果数据

我尝试使用 $http，但为什么它返回 null 结果？

angular.module('myApp')
.factory('sender', function($http) {
    var newData = null;
    $http.get('test.html')
        .success(function(data) {
            newData = data;
            console.log(newData)
        })
        .error(function() {
            newData = 'error';
        });
    console.log(newData)
    return newData
})

控制台说：http://screencast.com/t/vBGkl2sThBd4 http://screencast.com/t/vBGkl2sThBd4。为什么我的newData先是null然后又被定义了？怎样做才正确呢？

正如 YardenST 所说，$http是异步的，因此您需要确保依赖于您返回的数据的所有函数或显示逻辑$http.get()，得到相应的句柄。实现这一目标的一种方法是利用“承诺”$http返回：

笨蛋演示 http://plnkr.co/edit/9w2jTg?p=preview

var myApp = angular.module('myApp', []);

myApp.factory('AvengersService', function ($http) {

    var AvengersService = {
        getCast: function () {
            // $http returns a 'promise'
            return $http.get("avengers.json").then(function (response) {
                return response.data;
            });
        }
    };

    return AvengersService;
});


myApp.controller('AvengersCtrl', function($scope, $http, $log, AvengersService) {
    // Assign service to scope if you'd like to be able call it from your view also
    $scope.avengers = AvengersService;

    // Call the async method and then do stuff with what is returned inside the function
    AvengersService.getCast().then(function (asyncCastData) {
            $scope.avengers.cast = asyncCastData;
    });

    // We can also use $watch to keep an eye out for when $scope.avengers.cast gets populated
    $scope.$watch('avengers.cast', function (cast) {
        // When $scope.avengers.cast has data, then run these functions
        if (angular.isDefined(cast)) {          
            $log.info("$scope.avengers.cast has data");
        }
    });
});