Referencing another schema in Mongoose

Question

It sounds like the populate method is what your looking for. First make small change to your post schema:

var postSchema = new Schema({
    name: String,
    postedBy: {type: mongoose.Schema.Types.ObjectId, ref: 'User'},
    dateCreated: Date,
    comments: [{body:"string", by: mongoose.Schema.Types.ObjectId}],
});

Then make your model:

var Post = mongoose.model('Post', postSchema);

Then, when you make your query, you can populate references like this:

Post.findOne({_id: 123})
.populate('postedBy')
.exec(function(err, post) {
    // do stuff with post
});

Addendum: No one mentioned "Populate" --- it is very much worth your time and money looking at Mongooses Populate Method : Also explains cross documents referencing

http://mongoosejs.com/docs/populate.html

Late reply, but adding that Mongoose also has the concept of Subdocuments

With this syntax, you should be able to reference your userSchema as a type in your postSchema like so:

var userSchema = new Schema({
    twittername: String,
    twitterID: Number,
    displayName: String,
    profilePic: String,
});

var postSchema = new Schema({
    name: String,
    postedBy: userSchema,
    dateCreated: Date,
    comments: [{body:"string", by: mongoose.Schema.Types.ObjectId}],
});

Note the updated postedBy field with type userSchema.

This will embed the user object within the post, saving an extra lookup required by using a reference. Sometimes this could be preferable, other times the ref/populate route might be the way to go. Depends on what your application is doing.