如何使用promise避免回调地狱？[副本]

Question

{
  id: String,
  comments: [String], # id of Comments
  links: [String], #id of Links
}

按ID找到一个有评论和链接属于它的帖子：

Posts.findOne({id: id}, function(post) {
  Comments.find({id: post.id}, function(comments) {
    Links.find({id: post.id}, function(links) {
      res.json({post: post, comments: comment, links: links})
    })
  })
})

如何使用Promise（http://mongoosejs.com/docs/promissies.html）避免回拨地狱？

var query = Posts.findOne({id: id});
var promise = query.exec();

promise.then(function (post) {
  var query1 = Comments.find({id: post.id});
  var promise1 = query1.exec();
  promise1.then(function(comments) {
    var query2 = Links.find({id: post.id});
    var promise2 = query2.exec();
    promise2.then(function(links) {
      res.json({post: post, comments: comment, links: links})
    })
  })
});

好像不好......

Answer 1

尝试以下内容：

function getPost(id) {
  return Post
    .findOne({id: id})
    .then( post => {
      return post;
    });
}

使用Q模块

function getCommentsAndLinks(post) {
  return Q.all([
    Comment.find({id: post.id}),
    Links.find({id: post.id})
  ])
  .done( results => {
    let comments = results[0];
    let links = results[1];
    return [post, comments, links];
  })
  .catch( err => {
  // handle err
  })

在控制器上

getPost(postId)
.then(getCommentsAndLinks)
.then( results => {
  let post = results[0];
  let comments = results[1];
  let links = results[2];
  // more code here
})
.catch( err => {
// handle err
}) 

Post
.findOne({id: id})
.populate('comments')
.populate('links')
.then( post => {
    // here have the post with data of comments and links
});