Sub-document saving is not updating parent - node.js

Question

I'm trying to learn some relationship mechanics in mongoose. I have two models, a parent and a child:
var childrenSchema = new Schema({
name : String,
date : {type : Date, default: Date.now},
attribute1 : String,
attribute2 : String,
})
var parentSchema = new Schema({
name: String,
children: [childrenSchema]
})
exports.parent = mongoose.model('Parent', parentSchema);
exports.children = mongoose.model('Person', childrenSchema);
I will create a parent object in an initial call, and send an asynchronous call to an api which fetches children information based on the child's name. While that async call is out, I return the parent as is, because the user doesn't need to see the children's information immediately.
var Parent = require('schema.js').parent;
var Child= require('schema.js').children;
function addParent(p){
var parent = new Parent();
parent.name = p.result.name;
var child = new Child();
child.name = p.result.childname;
parent.children.push(child);
getChildDetails(child); // Async function to get children info..
parent.save(); //Save the parent so the information we return is persisted.
return parent; //Children probably not fully populated here. Not a problem.
}
function getChildDetails(child){
var promiseapi = require('mypromiseapi');
promiseapi.fetch('childinfo',child.name).then(function(result){
child.attribute1 = result.attribute1;
child.attribute2 = result.attribute2;
}).then( function(){
child.save(); // I expect the parent's information to be updated.
});
}
However, I am now in a little bit of a desync issue. Parent object has the single child on it, but only name and some mongoose specific information is populated (objectId). A child table is created also, with the child information fully populated, and it has the same objectID as the child that's affixed to the parent.
Why does the object that is affixed to the parent not get updated when I save it independently elsewhere in my code?

Answer 1

I solved it by using Populations (http://mongoosejs.com/docs/populate.html) instead of the pure schemas. The new schema models look like this:
var childrenSchema = new Schema({
name : String,
date : {type : Date, default: Date.now},
attribute1 : String,
attribute2 : String,
})
var parentSchema = new Schema({
name: String,
children: [{type: Schema.Types.ObjectId, ref:'Child'}]
})
And the new addParent method looks like this:
function addParent(p){
var parent = new Parent();
parent.name = p.result.name;
var child = new Child();
child.name = p.result.childname;
parent.children.push(child._id);
child.save();
getChildDetails(child); // Async function to get children info..
parent.save(function(err,result){
Parent.populate(result,{path:'children'},function(err,resultparent){
return(result);
});
}); //Save the parent so the information we return is persisted.
}