angular js上传文件功能不能正常工作

<input type="file" file-model="myFile" />

app.directive('fileModel', ['$parse', function($parse) {
    return {
        restrict: 'A',
        link: function(scope, element, attrs) {
            var model = $parse(attrs.fileModel);
            var modelSetter = model.assign;

            element.bind('change', function() {
                scope.$apply(function() {
                    modelSetter(scope, element[0].files[0]);
                });
            });
        }
    };
}]);

app.controller('MyController', ['$scope', '$http', function($scope, $http) {
    $scope.uploadFile = function() {
        var file = $scope.myFile;
        var formData = new FormData();
        formData.append('file', file);

        $http.post('/upload', formData, {
            transformRequest: angular.identity,
            headers: { 'Content-Type': undefined }
        }).then(function(response) {
            // 处理上传成功后的逻辑
        }, function(error) {
            // 处理上传失败后的逻辑
        });
    };
}]);