Handle schema references on mongoose - node.js

Question

I'm trying to define a simple RESTful API using Node.js, mongoose and restify. The goal is to have users which can comment on profiles of others users. For this I have a comment endpoint that receives a text, the author and the target of the comment (other user).
I want to reference users so I defined next schemas:
User schema:
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var UserSchema = new Schema({
"username": { type: String, unique: true, required: true },
"password": { type: String, required: true },
"comments": [{ type: Schema.Types.ObjectId, ref: 'Comment' }]
});
mongoose.model('User', UserSchema);
Comment schema:
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var CommentSchema = new Schema({
date: { type: Date, default: Date.now },
text: { type: String, required: true },
author: { type: mongoose.Schema.Types.ObjectId, ref: "User", required: true },
target: { type: mongoose.Schema.Types.ObjectId, ref: "User", required: true }
});
mongoose.model('Comment', CommentSchema);
I also have this controller (just showing createComment function):
exports.createComment = function(req, res, next) {
var authorId, targetId;
User.findOne({ _id: req.params.authorId}, function(err, author) {
if (author) {
User.findOne({ _id: req.params.targetId}, function(err, target) {
if (target) {
var comment = new Comment();
comment.text = req.params.text;
comment.author = author._id;
comment.target = target._id;
comment.save(function(err, comment) {
if (err) {
res.status(500);
res.json({
type: false,
data: 'Error occurred: ' + err
});
} else {
res.json({
type: true,
data: comment
});
}
});
} else {
res.json({
type: false,
data: 'User ' + req.params.authorId + ' not found'
});
}
});
} else {
res.json({
type: false,
data: 'User ' + req.params.targetId + ' not found'
});
}
});
};
So, I have three questions:
Why do I need to check if the user received exists? I would like to receive only the id and store it but I have to do two more queries to check it myself.
What I have to do to store in User only comments where that user is the target? solved in the edited code
How can I simplify this code? Is a pain to have async queries executed in order. I would like to have generic errors and not to have to handle each one.
EDIT: I've simplified the code using validations on the schema:
Comment schema:
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var User = mongoose.model('User');
var CommentSchema = new Schema({
date: { type: Date, default: Date.now },
text: { type: String, required: true },
author: { type: Schema.Types.ObjectId, ref: "User", required: true },
target: { type: Schema.Types.ObjectId, ref: "User", required: true }
});
CommentSchema.path('author').validate(function(value, respond) {
User.findOne({ _id: value}, function(err, user) {
respond(!err && user);
});
}, 'Author doesn\'t exists');
CommentSchema.path('target').validate(function(value, respond) {
User.findOne({ _id: value}, function(err, user) {
respond(!err && user);
});
}, 'Target user doesn\'t exists');
mongoose.model('Comment', CommentSchema);
Controller:
exports.createComment = function(req, res, next) {
var comment = new Comment(req.body);
comment.save(function(err, comment) {
if (err) {
res.status(500);
res.json({
type: false,
data: 'Error occurred: ' + err
});
} else {
User.findOne({ _id: comment.target }, function(err, user) {
user.comments.push(comment);
user.save();
});
res.json({
type: true,
data: comment
});
}
});
};
The problem with this is that now I have to use _id on queries (I would like to use a custom id) and I'm doing three queries every time I want save a comment (2 for validation and one more to store the comment). Is there a better way to to this?

Answer 1

You can use the select option of query in mongo to select only the _id field of the user, like this:
User.findOne({_id:req.params.authorId}).select({_id:1}).exec(function(err,user) {})
After you pull the userTarget from mongo, you need to add the comment._id to his list of comments, and save him:
target.comments.push(comment._id);
target.save(function(err, targetAfterSaved) {})
read about async or q, they are my favorites Libraries to handle with async functions. For handle with errors like you want, you can add some listeners - here is the documentation from restify site.
Hope you understand, if you need any help let me know