Mongoose objectId is not saving in another collection - node.js

Question

I am new to mongoose and nodejs. Please help me to understand what is wrong in my code while saving collection. My user.js looks like below
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var bcrypt = require('bcrypt-nodejs');
var UserSchema = new Schema ({
name: { type: String, required: true },
username:{ type:String, required: true, index:{ unique: true}},
password:{ type: String, required: true, select: false},
email:{ type: String, required: true, select: true},
mobile:{ type: String, required: true, select: true},
nativecid:{ type: Schema.Types.ObjectId, ref:'City'},
regdate:{ type: Date, default: Date.now },
did:{ type: String, required: false }
});
UserSchema.pre('save', function(next){
var user = this;
if(!user.isModified('password')) return next();
bcrypt.hash(user.password, null, null, function(err, hash){
if(err) return next(err);
user.password = hash;
next();
});
});
UserSchema.methods.comparePassword = function(password){
var user = this;
return bcrypt.compareSync(password, user.password);
};
module.exports = mongoose.model('User', UserSchema);
And my City model ie city.js looks like below
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var CitySchema = new Schema({
name: { type: String, required: true },
status: { type: Boolean, default: true },
date: { type: Date, default: Date.now }
});
module.exports = mongoose.model( 'City', CitySchema );
City is already stored in database as below
{ "_id" : ObjectId("56a4a0adb0f445561cfd4e37"), "name" : "New York", "date" : ISODate("2016-01-24T10:00:13.220Z"), "status" : 1, "__v" : 0 }
I want this ObjectId of New York should be saved in user collection while user signups. I am trying like below but not succeed.
var User = require('../models/user');
var City = require('../models/city');
api.post('/signup', function(req, res){
var user = new User({
name: req.body.name,
username: req.body.username,
password: req.body.password,
email: req.body.email,
mobile: req.body.mobile
});
City
.findOne({ name: "New York" })
.populate('_id')
.exec(function (err, city1) {
if(err){
res.send(err);
return;
}
console.log('The creator is %s', city1.name);
return user.nativecid = city1._id;
})
user.save(function(err){
if(err){
res.send(err);
return;
}
res.json({
success: true,
message: 'User created successfully!'
});
});
});
I am not understanding what is wrong. Please advice me.

Answer 1

Just save user in city.findOne (nested) and may be no need to populate you should use projection.
City.findOne({ name: "New York" }, {name:1}) // ID return defaulat
.exec(function (err, city1) {
if(err){
res.send(err);
return;
}
console.log('The creator is %s', city1.name);
user.nativecid = city1._id;
user.save(function(err1){
if(err1){
res.send(err1);
return;
}
res.json({
success: true,
message: 'User created successfully!'
});
});
})