一对多猫鼬-不太清楚如何实施

Question

I'm relatively new to Mongoose (2 days at it) and I want to make a one-to-many relationship, as in one person can come from one country, one country has many people.

So, this is what I've got:

    var userSchema = new Schema({
    name: String,
    username: {
        type: String,
        required: true,
        unique: true
    },
    password: {
        type: String,
        required: true
    },  
    country: {
        type: Schema.Types.ObjectId,
        ref: 'Country'
    }

});
var User = mongoose.model('Person', userSchema);

var countrySchema = new Schema({
    name: {
        type: String,
        required: true,
        unique: true
    },
    created_at: Date,
    updated_at: Date,
    people: [{
        type: Number,
        ref: 'User'
    }]
});

var Country = mongoose.model('Country', countrySchema);

var UK = new Country({
    name: 'UK'
});


usa.save(function(err) {
    var user = new User({
        username: 'James',
        password: 'Bond',
        country: UK._id
    });

    user.save(function(err) {

    });

});

Now I have two questions: 1) I've seen that ref can sometimes be an ObjectId or just a number - what's the differences? 2) when saving the data, in my case, I saved country to a person (by _id), how do I save a person to a country? Should I update the instance of the model?

Thanks

UPDATE:

since this question has been marked as a duplicate, let me rephrase the question: consider the official example in this link: http://mongoosejs.com/docs/populate.html The idea is that one person has many stories, and one story has one author (person). So, the saving would be as follows:

    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!
  });
}); 

That's from the official documentation - my question is, where or how do we save story1 to the Author ? Author is created before the Story , so, shouldn't the Author be updated with story1._id ???

UPDATE 2:

I figured out that if I use only type: Schema.Types.ObjectId and never type: Number , that I can do just this:

    var aaron = new Person({ _id: 0, name: 'Aaron', age: 100 });
var story1 = new Story({
    title: "Once upon a timex.",
    _creator: aaron._id    // assign the _id from the person
});
aaron.stories.push(story1._id);

aaron.save(function (err) {
  if (err) return handleError(err);
}); 
story1.save(function (err) {
    if (err) return handleError(err);
    // thats it!
}); 

This actually works in a dummy example... are there any problems if there were too many posts in a request that IDs could have get lost/duplicated? What is the shortcoming of this approach?

Answer 1

1) I've seen that ref can sometimes be an ObjectId or just a number - what's the differences?

Please refer to this question Why do they use an ObjectId and a Number in the Mongoose Population example?

where or how do we save story1 to the Author

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);
    // save id of story1 into person here, also you should use `update` operation with `$push` operator.
    aaron.stories.push(story1._id);
    aaron.save(function(err){
        if (err)
            handleError(err);
        else
            console.log('save person successfully...');
    })
  });
});

The results

> db.stories.find()
{ "_id" : ObjectId("56f72f633cf1e6f00159d5e7"), "title" : "Once upon a timex.", "_creator" : 0, "fans" : [ ], "__v" : 0 }
> db.people.find()
{ "_id" : 0, "name" : "Aaron", "age" : 100, "stories" : [ ObjectId("56f72f633cf1e6f00159d5e7") ], "__v" : 1 }