robinjmetcalfe / eloquent-triple-pivot

Laravel/Eloquent triple model many-to-many relation

Triple Pivot

A way to link 3 many-to-many relations together in Laravel 4's Eloquent.

---

Contents

Usage

Setup

1. Create 3 models: User, Tag, Track
2. Set up your tables (users, tags, tracks, users_tags_tracks)
3. Require in composer.json and config/app.php
4. Add the trait in all 3 models
5. Define the relation method as ->tripleBelongsToMany()
6. (Optional) Create a nice-name relation for the ->third() method

---

Usage

// Get the first User, and autoload their tags
$user = User::with( 'tags' )->first();

// Like an ordinary belongsToMany
$user->tags; // Collection of tags
$user->tags->first(); // Tag model

// Get the track associated with a given tag for the user
$user->tags->first()->third; // Track model
$user->tags->first()->track; // Track model (only if you did step 6)

// Attach a tag/track to a user
$user->tags()->attach( [ $tagId, $trackId ] ); // Pass an array of 2 IDs
$user->tags()->attach( [ Tag::find( $tagId ), Track::find( $trackId ) ] ); // Pass an array of 2 models

---

Setup

1. Create 3 models

Models/User.php (should already exist)

<?php

namespace Models;	
class User extends \Eloquent {
}

Models/Tag.php

<?php

namespace Models

class Tag extends \Eloquent {
}

Models/Track.php

<?php

namespace Model;

class Track extends \Eloquent {
}

2. Set up the database tables

database/migrations/1_0_0_0_create_triple_pivot_tables.php: Create the tables we're going to be joining together (users may already have a migration).

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;

class CreateTriplePivotTables extends Migration {

	public function down() {
		Schema::drop( 'users' );
		Schema::drop( 'tags' );
		Schema::drop( 'tracks' );
		Schema::drop( 'users_tags_tracks' );
	}

	public function up() {
		Schema::create( 'users', function ( Blueprint $table ) {
			$table->increments('id');
			$table->string('email');
		} );
	
		Schema::create( 'tags', function ( Blueprint $table ) {
			$table->increments('id');
			$table->string('name');
		} );
	
		Schema::create( 'tracks', function ( Blueprint $table ) {
			$table->increments('id');
			$table->string('name');
		} );

		Schema::create( 'users_tags_tracks', function ( Blueprint $table ) {
			$table->integer( 'user_id' )->unsigned()->nullable();
			$table->integer( 'tag_id' )->unsigned()->nullable();
			$table->integer( 'track_id' )->unsigned()->nullable();
		} );
	}

}

Require the package

composer.json: Add in the package definition.

"require": {
    "laravel/framework": "4.2.*",
    ...
    "jarektkaczyk/eloquent-triple-pivot": "dev-master"
},

Run composer update -o in the Terminal.

config/app.php: Add the service provider to the providers array.

'providers' => array(

	'Illuminate\Foundation\Providers\ArtisanServiceProvider',
	...
	'Jarektkaczyk\TriplePivot\TriplePivotServiceProvider',

),

4. Add the trait into all of our models

Models/User.php: Two use statements - one to pull in the namespaced Trait, one to use it in the Model.

<?php

namespace Models;
use Jarektkaczyk\TriplePivot\TriplePivotTrait;

class User extends \Eloquent {
	use TriplePivotTrait;
}

Models/Tag.php: As above

<?php

namespace Models;
use Jarektkaczyk\TriplePivot\TriplePivotTrait;

class Tag extends \Eloquent {
	use TriplePivotTrait;
}

Models/Track.php: As above

<?php

namespace Models;
use Jarektkaczyk\TriplePivot\TriplePivotTrait;

class Track extends \Eloquent {
	use TriplePivotTrait;
}

5. Define the tripleBelongsToMany relation

Models/User.php

<?php

namespace Models;
use Jarektkaczyk\TriplePivot\TriplePivotTrait;

class User extends \Eloquent {
	use TriplePivotTrait;
	
	/**
	 * @return \Jarektkaczyk\TriplePivot\TripleBelongsToMany
	 */
	public function tags() {
		return $this->tripleBelongsToMany( 'Models\Tag', 'Models\Track', 'users_tags_tracks' );
	}
}

6. (Optional) Define a nicer method than ->third on Models/Tag

Models/Tag.php: Create a new method getTrackAttribute() which forwards on to the getThirdAttribute() method so we can call $tag->track->name instead of $tag->third->name.

<?php

namespace Models;
use Jarektkaczyk\TriplePivot\TriplePivotTrait;

class Tag extends \Eloquent {
	use TriplePivotTrait;

	/**
	 * @return \Illuminate\Database\Eloquent\Model
	 */
	public function getTrackAttribute() {
		return $this->getThirdAttribute();
	}
}