php – laravel 4重定向到2个参数的路由

public function store($username,$courseId)
{       
        if (Auth::user()->username == $username && Auth::user()->courses()->where('id','=',$courseId)->first() != null){
        $course = Course::find($courseId);
        $forum = new Forum();
        $forum->description = Input::get('description');
        $forum->course_id   = Input::get('course_id');
        $forum->save();
        return Redirect::to(route('users.courses.forums.index',Auth::user()->username,$course->id));
        }
    return Redirect::to('/');
}

Redirect中的参数不起作用. Store是ForumController中的POST方法. Store收到的参数是正常的,因为我没有验证’if’的问题.我可以创建一个论坛并保存它,但当我尝试重定向时,我有这个错误

Trying to get property of non-object

而users.courses.forums.index是我的URI与Action ForumController @ index的名称.最后一个方法需要2个参数($username,$courseid).像这样

public function index($username,$courseId)
{       
        $course = Course::find($courseId);
        $forum = DB::table('forums')->where('course_id',$course->id)->get();
        return View::make('forums.index',compact('course','forum'));    
}