Advanced custom schema type for custom objects or value-objects

I couldn’t find any example of an advanced custom schema type involving custom objects (or value-objects) in Mongoose >=4.4.

I already posted a question on StackOverflow without success: http://stackoverflow.com/questions/38094817/mongoose-advanced-custom-schema-object-type.

Resuming, how can I achieve that:

1. Every time a new model is “hydrated” from db (mongoose init), the field will be an instance of my custom object and not a plain object. For this I understand it will use the SchemaType.prototype.cast function.
2. Every time I will save my Model the custom type field should be encoded and stored in a custom way (as plain object, array, string or any BSON type).
3. If I use model.toObject() it will recursively call the model.myfield.toObject() to have a full plain object representation of the document.

[vkarpov15]

I added the toBSON() check in 1a93d1f. Here’s a better example of how to do the polygon type you’re looking at:

'use strict';

var assert = require('assert');
var mongoose = require('mongoose');
var Schema = mongoose.Schema;

mongoose.connect('mongodb://localhost/gh4356');
mongoose.set('debug', true);

class Polygon {
  constructor(v) {
    this.v = v;
  }

  toBSON() {
    return this.v;
  }
}

class PolygonSchema extends mongoose.SchemaType {
  cast(v) {
    return new Polygon(v);
  }
}

mongoose.Schema.Types.Polygon = PolygonSchema;

const schema = new Schema({ test: Polygon });
const M = mongoose.model('Test', schema);

M.create({ test: 5 }).then(doc => {
  console.log('done', doc);
  console.log(doc.test.toBSON());
  process.exit(0);
});

Output:

$ node gh-4356.js 
(node:14709) DeprecationWarning: Mongoose: mpromise (mongoose's default promise library) is deprecated, plug in your own promise library instead: http://mongoosejs.com/docs/promises.html
Mongoose: tests.insert({ test: 5, _id: ObjectId("581e684cc4d5933975526934"), __v: 0 })
done { __v: 0, test: Polygon { v: 5 }, _id: 581e684cc4d5933975526934 }
5

[vkarpov15]

@NikhilAshodariya I opened up a separate issue for this #6174.