Mongoose: Advanced custom schema type for custom objects or value-objects

[dario1985]

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]

1. Yep, cast()
2. Give your Polygon class a toBSON() function https://mongodb.github.io/node-mongodb-native/driver-articles/anintroductionto1_1and2_2.html#tobson-method
3. It should already do this, no?

[dario1985]

Thank you for the reply!

Give your Polygon class a toBSON() function https://mongodb.github.io/node-mongodb-native/driver-articles/anintroductionto1_1and2_2.html#tobson-method

Yes, it work. But the debug logs of Mongoose seem to don't call it and shows it wrong (object instead of array):

Mongoose: shapes.update({ _id: ObjectId("...") }) { '$set': { bounds: { ... } } }
Trace: CALLING toBSON: [ /* array data */ ]
    at Polygon.toBSON (/var/www/test/polygons.js:136:47)
    at serializeInto (/var/www/node_modules/mongoose/test/node_modules/bson/lib/bson/parser/serializer.js:664:23)
    at serializeObject (/var/www/test/node_modules/bson/lib/bson/parser/serializer.js:280:18)
    at serializeInto (/var/www/test/node_modules/bson/lib/bson/parser/serializer.js:705:17)
    at serialize (/var/www/test/node_modules/bson/lib/bson/bson.js:47:27)
    ...
    at Collection.update (/var/www/test/node_modules/mongoose/node_modules/mongodb/lib/collection.js:1041:44)
    at NativeCollection.(anonymous function) [as update] (/var/www/test/node_modules/mongoose/lib/drivers/node-mongodb-native/collection.js:125:28)
    at model.Model.$__handleSave (/var/www/test/node_modules/mongoose/lib/model.js:161:23)
    at model.Model.$__save (/var/www/test/node_modules/mongoose/lib/model.js:185:9)
    at model.Model.save (/var/www/test/node_modules/mongoose/lib/model.js:283:15)
    at model._done (/var/www/test/node_modules/hooks-fixed/hooks.js:101:24)
    at _next (/var/www/test/node_modules/hooks-fixed/hooks.js:64:28)
    at fnWrapper (/var/www/test/node_modules/hooks-fixed/hooks.js:186:18)
    at model.Object.defineProperty.value.fn (/var/www/test/node_modules/mongoose/lib/schema.js:220:11)
    at _next (/var/www/test/node_modules/hooks-fixed/hooks.js:62:30)
    at fnWrapper (/var/www/test/node_modules/hooks-fixed/hooks.js:186:18)
    at /var/www/test/node_modules/mongoose/lib/schema.js:201:17
    at /var/www/test/node_modules/mongoose/node_modules/kareem/index.js:127:16
    at process._tickDomainCallback (node.js:381:11)

It should already do this, no?

No, I tried to call the toObject() on the main model and it don't call it on the custom type.

[vkarpov15]

Ok will make sure that debug logs handle .toBSON() and .toObject() will work for the custom type, thanks for pointing this out

[dario1985]

Thank you!

[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

[NikhilAshodariya]

I couldn't find any example for storing a composite object in MongoDB using Mongoose and retrieving the inner object with all the methods without typecasting.

I already posted a question on StackOverflow:
https://stackoverflow.com/questions/48960604/how-to-store-composite-object-in-mongodb-using-mongoose

Please help.

[vkarpov15]

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