Mongoose schema for array of sub-documents ids from a different collection

Question

I have a schema like this for a family (whose children are enrolled in a school)...

var familySchema = new Schema({
    parents: [{
        firstName: String,
        lastName: String,
        email: String,
    }],
    students: [{
        firstName: String,
        lastName: String,
        grade: Number,
    }]
});

I'd like to describe many schools that contain classrooms, and have the classrooms contain students, something like this...

var schoolSchema = new Schema({
    name: String,
    street: String,
    classrooms: [{
        classroomNumber: Number,
        students: [ /* I am mixed up here */ ]
    }]
});

How do I tell mongoose that I want an array of object ids for students found in the other collection?

I understand from this answer that, if I wanted the classrooms to refer to family documents, I could say something like:

families: { type : ObjectId, ref: 'Family' }

but how do I do the same for sub-documents of another collection? (If it isn't obvious, I'm just learning both mongo and mongoose).

zangw · Accepted Answer · 2016-02-17 04:17:02Z

1

If you want to use sub-documents reference, you need to change your reference to the 'student' array.

var studentSchema = new Schema({
    firstName: String,
    lastName: String,
    grade: Number,
});

var familySchema = new Schema({
    parents: [{
        firstName: String,
        lastName: String,
        email: String,
    }],
    students: [studentSchema]
});

var schoolSchema = new Schema({
    name: String,
    street: String,
    classrooms: [{
        classroomNumber: Number,
        students: [ { type: ObjectId, ref: 'Family.students' }]
    }]
});

var Student = mongoose.model('Student', studentSchema );  
var Family = mongoose.model('Family ', familySchema ); 
var School = mongoose.model('School', schoolSchema );

answered Feb 17, 2016 at 4:17

zangw

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4 Comments

user1272965 Over a year ago

Great answer. Thanks very much.

user1272965 Over a year ago

Hey - sorry to bother with a followup: I'm following a pattern where I have one file per model, and each model file says module.exports = mongoose.model('Model', ModelSchema); at the end. So, in my family.js, can I just call mongoose.model('Student'... on student and discard the result (so I can still export the family model)? And, in my school.js, must I require any other model files to use the syntax you suggest?

zangw Over a year ago

@user1272965, in each model file, you can use mongoose.model('Model', ModelSchema);, when you want to use this model file in other file, you should use var School = mongoose.model('School');, then this School could be use in this file... Hope I make myself clearly.

user3211705 Over a year ago

Using above method, when i use populate() in find - it returns error as 'Schema hasn't registered for model "Family.students"'

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