angularjs中My97DatePicker无法通过$scope.ngModel获取值解决

1、写一个angular自定义指令Directive（网上找的）

/*my97DatePicker指令*/
angular.module('activitiModeler').directive('datePicker', function () {
    return {
        restrict: 'A',
        require: 'ngModel',
        scope: {
            minDate: '@',
        },
        link: function (scope, element, attr, ngModel) {
        	//
            element.val(ngModel.$viewValue);
            //
            function onpicking(dp) {
                var date = dp.cal.getNewDateStr();
                scope.$apply(function () {
                    ngModel.$setViewValue(date);
                });
            }
            //
            element.bind('click', function () {
                WdatePicker({
                    onpicking: onpicking,
                    dateFmt: 'yyyy-MM-dd HH:mm',
                    minDate: (scope.minDate || '%y-%M-%d %H:&m'),
                })
            });
            //
        }
    };
});

2、以指令方式使用My97DatePicker---- date-picker