An Introduction to Mongoose

The flexibility of MongoDB has a weakness: there's no protection against entering data in any arbitrary format, and no validation of any sort. Mongoose helps with those problems.

Objectives

Use Mongoose to help validate data to be stored in MongoDB
Use Mongoose as an object-document mapper within a JavaScript program

Instructions

Fork, clone, and npm install.

Mongoose is an Object-Document Mapper

What does that mean? We have objects in our JavaScript and documents in our MongoDB, and Mongoose bridges between them.

We'll learn about Mongoose by building a command line script. Think of the script as a similar to a controller and the Mongoose Models as the mechanism to access the data (ActiveRecord).

Mongoose has

Schemas that we use to create models.
Models - Constructors for documents
Documents - a mapping from MongoDB to JavaScript
Validations checks on our data.

We'll use these to create a command line crud app.

Schema

var mongoose = require('mongoose');

var peronsSchema = new mongoose.Schema({

  name: {
    given: String,
    surname: String
  }

});

Model

var Person = mongoose.model( 'Person', PersonSchema);

We'll use the models to interact with appropriately named collections of documents. Mongoose maps the model 'Person' to the MongoDB collection people.

Document

var person = Person.create({...});
// or
var person = new Person({...});
person.save();

Virtual attributes

We can add calculated attributes to the model too. These are called 'virtual attributes.' Assume we have name.given and name.surname properties: we can derive a name.full property from them.

personSchema.virtual('name.full').get(function () {
  return this.name.given + ' ' + this.name.surname;
});

personSchema.virtual('name.full').set(function (name) {
  var split = name.split(' ');
  this.name.given = split[0];
  this.name.surname = split[1];
});

Using models

We'll use Mongoose to query MongoDB:

var query = Person.findOne({ 'name.surname': 'Rollins' });
query.exec().then(function(person) {
    console.log('full name: %s, given: %s, surname %s',
        person.name.full, person.name.given, person.name.surname);
});

Validation

var contactSchema = new Schema({

    // given and surname are required

    name: {
      given: {
        type: String,
        required: true
      },
      surname: {
        type: String,
        required: true
      },
    },

    // title is not required

    title: String
});

References

The Mongoose API docs at http://mongoosejs.com/docs/api.html

HoldenMills / mongoose-crud