Relationships
=============

Parse classes are often related to one another. For example, a blog post may 
have many comments, or an order could be related to the user who placed it. 
Object model makes managing and working with these relationships easy, and 
supports several different types of relationships:

* One to One
* One to Many

One To One
----------

A one-to-one relationship is a very basic relation. For example, a `User` model 
might be associated with one `Test`. To define this relationship, we place a 
`test` method on the `User` model. The `test` method should call the `belongsTo` 
method and return its result:

.. literalinclude:: ../references/UserFinal.php
   :language: php

Next you will need to add a pointer field to your parse class:

.. image:: ../images/parse-pointer-test.png

By default Laravel-Parse expects that the field name is the same like the model 
name in lower-case (here: `App\\Test` => `test`). But you can change the key if 
you set a second argument to the `belongsTo` method:

.. code-block:: php

   public function test()
   {
     return $this->belongsTo('App\Test', 'related_test');
   }

Now you will be able to get the relationship using the `test` method:

.. code-block:: php

   $query = new Query('_User', 'App\User', true);

   $query = $query->findOrFail('TtlCRVV9ZK');

   return $query->test();

Should return something like the following:

.. image:: ../images/parse-pointer-test-result.png

One To Many
-----------

A "one-to-many" relationship is used to define relationships where a single model 
owns any amount of other models. For example, a blog post may have an infinite 
number of comments. Like all other Laravel-Parse relationships, one-to-many relationships 
are defined by placing a function on your object model:

.. literalinclude:: ../references/Post.php
   :language: php

Like before, the **first argument** will determine another object model that is 
related to your object model. The **second argument** can be used in order to 
determine the foreign key to use, in this case `comments`.

Now you can determine that a comment belongs to a post, like we have seen before:

.. literalinclude:: ../references/Comment.php
   :language: php

In Parse you will need to create a `Post` class and a `Comment` class. The 
`Post` class will need a relation field:

.. image:: ../images/parse-post-comment-relation.png

And the `Comment` class will need a pointer field:

.. image:: ../images/parse-comment-post-pointer.png

Now you will be able to get the relationship using the `post` or `comments` method:

.. code-block:: php

   $query = new Query('Comment', 'App\Comment', true);
   
   $query = $query->findOrFail('AM0iE0ISMj');
   
   dd($query->post());
   
   // or

   $query = new Query('Post', 'App\Post', true);
   
   $query = $query->findOrFail('zJFlef2kcU');
   
   dd($query->comments());