使用Mongoose和Express.js进行MVC的OOP

Question

I'm creating an Express.js app in which I want to use the MVC pattern and Mongoose for the document mapping to a MongoDB database. I've created a folder for models and I want to derive everything from (Javascript's version of) abstract classes for better code organization.

I'm confused about what the best way is to organize the abstract classes and set default values that each instance of the models should be. For example, one way is to use Mongoose Schemas for abstract classes, and then use Mongoose models for the models themselves:

Feline.js:

var mongoose = require('mongoose');

var Feline = mongoose.Schema({
  size: 'Number'
});

Feline.methods.getSize = function () {
  return this.size;
}

module.exports = Feline;

HouseCat.js:

var mongoose = require('mongoose')
, FelineSchema = require('./Feline.js');

var HouseCatModel = mongoose.model('HouseCat', FelineSchema)
, HouseCat = new HouseCatModel({
  size: 1 //Domesticated cats are small
});

module.exports = HouseCat;

There are a few problems with this design. For one, I would think there must be a better way to set specific properties for the each model without instantiating a new model object each time the client wants to create a new instance of a model type. For another, using this scheme, Mongoose has to be required in every model file, and the code is custom-tailored to use mongoose, which means it will be difficult to switch to another ODM if we want to do that in the future.

Is there any better way of coding this? And is there any design pattern which is easy enough to implement in Node that will allow for easy changing of the ODM?

Answer 1

As mongoose is specific to mongodb, this will be a hard task to abstract its behaviour.

The easiest way to do it is to set an interface for all ODMs and use an adapter pattern where mongoose is an "adaptee". Then, you can use a module providing some dependency injection to replace the used ODM.

As it is a really long task, I cannot give you some code. Moreover, it may be a pain to implement that kind of thing in javascript because it does not provide strong OOP natively. However, I can suggest you to take a look at some frameworks which can help you to do that like Danf for instance which provides a strong OOP paradigm with interfaces, classes, inheritance and a powerful dependency injection.