mongoose's documentation example for population, gives an error - node.js

Question

i had this problem in my own code. i copied the code from the example at Mongoose Query Population to see what am i doing wrong. but i have the same problem with their code too.
the problem is about the log in the exec callback:
console.log('The creator is %s', story._creator.name);
^
TypeError: Cannot read property '_creator' of null
and here is the code.
var mongoose = require('mongoose'),
Schema = mongoose.Schema
var personSchema = Schema({
_id : Number,
name : String,
age : Number,
stories : [{ type: Schema.Types.ObjectId, ref: 'Story' }]
});
var storySchema = Schema({
_creator : { type: Number, ref: 'Person' },
title : String,
fans : [{ type: Number, ref: 'Person' }]
});
var Story = mongoose.model('Story', storySchema);
var Person = mongoose.model('Person', personSchema);
now using the models, making a new Person and saving it. and also saving a story and making the _creator of it to be equal to the id of the Person model, called aaron
var aaron = new Person({ _id: 0, name: 'Aaron', age: 100 });
aaron.save(function (err) {
if (err) return handleError(err);
var story1 = new Story({
title: "Once upon a timex.",
_creator: aaron._id // assign the _id from the person
});
story1.save(function (err) {
if (err) return handleError(err);
// thats it!
});
});
Story
.findOne({ title: 'Once upon a timex.' })
.populate('_creator')
.exec(function (err, story) {
if (err) return handleError(err);
console.log('The creator is %s', story._creator.name);
// prints "The creator is Aaron"
});
UPDATE:
in database i have only one collection called poeple with only one document:
{
"_id": 0,
"name": "Aaron",
"age": 100,
"stories": [],
"__v": 0
}
the code does not have the world people in it so where the collection name comes from? i'm confused.
thanks for any help you are able to provide.

Answer 1

The story1 is saved until the callback function of it is called. Please try to move the Stroy.find into the callback function of story1.save as below.
story1.save(function (err) {
if (err) return handleError(err);
Story
.findOne({ title: 'Once upon a timex.' })
.populate('_creator')
.exec(function (err, story) {
if (err) return handleError(err);
console.log('The creator is %s', story._creator.name);
// prints "The creator is Aaron"
});
});