Using ORM classes directly from the controller in MVC, bad practice?

Question

I've recently delved into using an ORM in my CodeIgniter application and one i've gone for is Propel. Now this gives me the power to basically use Propels classes as the 'Model' but is this bad practive?

So my controller code would be as follows:

<?php
    class Page extends Controller {
        function __construct() {
            parent::__construct();  
        }   

        function index() {
            $foo = FooQuery::create()->limit(10)->find();
            $data['content'] = array('foo'=>$foo);
            $this->load->view('home', $foo);    
        }
    }
?>

I want to solve this issue before I carry on developing my application. An example of how I should do this would be very helpful if you do consider this to be bad practice please.

Thanks in advance

Answer 1

Yes, it's bad practice.

The model should contain all of your data logic and abstract it all away from the rest of the program. To the rest of the application, the models should look like black boxes out of which it gets its data. If you use an ORM as your model, you're leaking the abstraction and tightly coupling your controller to your data layer.

Instead, create your models, and deal with the ORM in there. That way if you ever need to adjust your data model, you can just change it in one place (the model layer) and know that the abstraction will hold.

Answer 2

With the Query classes Propel now uses, I think the difference with a more "formal" Model becomes smaller and smaller. If this will become a library that you release into the world it would be an advantage to have an abstraction layer so you can have different backends, but if it is an in-house application I would just use the Query classes as your Model.

But remember that the Query classes are created to feel like an actual object, and that they hide the relational part as much as they can. You can use this to your advantage. Check out this article about rewriting your SQL queries with Query methods, especially the third answer: move more and more into your Query class, so your Controller doesn't feel like it uses a database.

// Instead of this code in your controller,
// tightly coupled to your database logic
$books = BookQuery::create()
   ->filterByTitle('%war%')
   ->filterByPrice(array('max' => 10)
   ->filterByPublishedAt(array('max' => time()))
   ->leftJoin('Book.Author')
     ->where('Author.Name > ?', $fameTreshold);

// You would use this code in your controller
// and create small methods with the business logic in the BookQuery class
$books = BookQuery::create()
  ->titleContainsWord('war')
  ->cheap()
  ->published()
  ->writtenByFamousAuthors();