无法返回collection.findOne（）

Question

我正在使用Monk这是一个mongodb驱动程序，我想返回collection.findOne（）的值来渲染 mypost 作为响应参数。

这是我的代码：

//show single post
router.get('/show/:id', function(req, res, next){
    var mycategories = []
    var mypost = {};
    var posts = db.get('posts');
    var categories = db.get('categories');
    posts.findOne({_id: req.params.id}, function(err, post){

        });
     console.log(mypost);

    categories.find({}, {}, function(err, categories) {
        for (i=0; i<categories.length; i++) {
              mycategories[i] = categories[i];
            }
    });
    res.render('show', {
            'pageTitle': mypost.title,
            'categories': mycategories,
            'post': mypost

        });

Answer 1

//show single post
router.get('/show/:id', function(req, res, next){
  var mycategories = []
  var mypost = {};
  var posts = db.get('posts');
  var categories = db.get('categories');
  posts.findOne({_id: req.params.id}, function(err, post){


    //success param is post not my post
   console.log(mypost, post);

   categories.find({}, {}, function(err, categories) {
    for (i=0; i<categories.length; i++) {
      mycategories[i] = categories[i];
    }

    //you cant get access to outside callback 

    res.render('show', {
      'pageTitle': post.title,
      'categories': mycategories,
      'post': post

    });

  });


 });


});