Mongoose Relationships

... because sometimes embedded documents aren't enough.

A plugin for Mongoose adding a simple syntax for model relationships and providing useful helpers to empower them.

This is an early release with limited functionalities. I'm looking for feedback on the API and features (been exploring a few different solutions, nothing's impossible!).

I'm inspiring from various libraries in Ruby I've used throughout the years. Might not be your cup of tea.

Goals

• Be unobtrusive and compliant with the ways of Mongoose (coding style, testing, API).

Usage

First, npm install mongo-relation.

Add relationships to your schema through either hasMany, belongsTo or habtm (has and belongs to many).

• {String} ModelName is the name of the Model.
• {Object} options
  • {String} through if you want to specify what path to use for the relationship. Else the path will be created for you by pluralizing the ModelName.
  • {String} dependent takes either "delete" or "nullify" and indicated what to do when the element is removed from the parent's through array.

var mongoose = require('mongoose');
require('mongo-relation');
 
YourSchema.hasMany('ModelName', {through: 'PathName', dependent: 'delete|nullify'});

It's good to take note that for "has and belongs to many" type relationships, the dependent option only deletes the reference, not the actual referenced document.

Examples

One to Many

UserSchema.hasMany('Post', {dependent: 'delete'});
 
// uses the 'author' path for the relation 
PostSchema.belongsTo('User', {through: 'author'});

Has and Belongs to Many

PostSchema.habtm('Category');
CategorySchema.habtm('Post');

Methods

Every Document that has their Schema plugged with mongo-relation has access to the following methods.

Let's use this starting point:

var mongoose = require('mongoose');
require('mongo-relation');
 
// UserSchema stores an Array of ObjectIds for posts 
var UserSchema = new mongoose.Schema({
    posts: [mongoose.Schema.ObjectId]
});
 
// PostSchema stores an ObjectId for the author 
var PostSchema = new mongoose.Schema({
    title  : String
  , author : mongoose.Schema.ObjectId
});
 
// Attach the plugin 
UserSchema.hasMany('Post');
PostSchema.belongsTo('User', {through: 'author'});
 
var User = mongoose.model('User', UserSchema)
  , Post = mongoose.model('Post', PostSchema);

create

Takes care of creating the child document and the links between it and the parent document.

• {Object|Array} objs representation of the child document(s) to create
• {Function} callback (optional) function returning an error if any, the new parent document and the created post(s)

Example:

var user = new User();
 
user.posts.create({
  title: "Mongoose, now with added love through relationships!"
}, function(err, user, post){
  // user.posts.length === 1 
  // post.title === "Mongoose, now with added love through relationships!" 
});
 
// Using an `Array` 
user.posts.create([
    { title: "Not too imaginative post title" }
  , { title: "... a tad more imaginative post title" }
], function(err, user, posts){
  // user.posts.length === 3 
  // posts.length == 2 
  // posts[0] instanceof Post 
});

build

Instantiates a child document, appends its reference to the parent document and returns the child document. Does not save anything.

• {Object} obj representation of the child document(s) to create

Example:

var post = user.posts.build({title: "Just instantiating me"});
// post.author === user._id 

append

Allows pushing of an already existing document into the parent document. Creates all the right references.

Works with either a saved or unsaved document.

The parent document is not saved, you'll have to do that yourself.

• {Document} child document to push.
• {Function} callback called with an error if any and the child document w/ references.

Example:

var post = new Post();
 
user.posts.append(post, function(err, post){
  // post.author === user._id 
  // user.posts.id(post._id) === post._id 
});

concat

Just like Array.prototype.concat, it appends an Array to another Array

• {Document} child document to push.
• {Function} callback called with an error if any and the child document w/ references.

Example:

var posts = [new Post(), new Post()];
 
user.posts.concat(posts, function(err, posts){
  // `posts` is an `Array` of `Document` 
  // each have its author set to `user._id` 
});

find

It's the same as a Mongoose.Query. Only looks through the children documents.

See Mongoose.Query for the params

Example:

user.posts.find({title: "Not too imaginative post title"}, function(err, posts){
  // posts.length === 1 
  // posts[0].author == user._id 
  // posts[0].title == "Not too imaginative post title"; 
});

populate

Some sugary syntax to populate the parent document's child documents.

• {Array} fields (optional) you want to get back with each child document
• {Function} callback called with an error and the populate document

Example:

user.posts.populate(function(err, user){
  // user.posts.length === 2 
});

remove

Depending on the dependent option, it'll either delete or nullify the

• {ObjectId} id of the document to remove
• {Function} callback (optional) called after the deed is done with an error if any and the new parent document.

Example:

user.posts.remove(user.posts[0]._id, function(err, user){
  // The post will either be delete or have its `author` field nullified 
});

Testing

Mongo-Relation uses Mocha with Should. Tests are located in ./test and should be ran with the make test command.

Contribute

• Pick up any of the items above & send a pull request (w/ passing tests please)
• Discuss the API / features in the Issues
• Use it and report bugs in the Issues (w/ failing tests please)