Models in the Zend Framework

Question

What are some of the ways you have implemented models in the Zend Framework?

I have seen the basic class User extends Zend_Db_Table_Abstract and then putting calls to that in your controllers:

$foo = new User;

$foo->fetchAll()

but what about more sophisticated uses? The Quickstart section of the documentation offers such an example but I still feel like I'm not getting a "best use" example for models in Zend Framework. Any interesting implementations out there?

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EDIT: I should clarify (in response to CMS's comment)... I know about doing more complicated selects. I was interested in overall approaches to the Model concept and concrete examples of how others have implemented them (basically, the stuff the manual leaves out and the stuff that basic how-to's gloss over)

Solution 1

I personally subclass both Zend_Db_Table_Abstract and Zend_Db_Table_Row_Abstract. The main difference between my code and yours is that explicitly treat the subclass of Zend_Db_Table_Abstract as a "table" and Zend_Db_Table_Row_Abstract as "row". Very rarely do I see direct calls to select objects, SQL, or the built in ZF database methods in my controllers. I try to hide the logic of requesting specific records to calls for behind Zend_Db_Table_Abstract like so:

class Users extends Zend_Db_Table_Abstract {

    protected $_name = 'users';

    protected $_rowClass = 'User'; // <== THIS IS REALLY HELPFUL

    public function getById($id) {
        // RETURNS ONE INSTANCE OF 'User'
    }

    public function getActiveUsers() {
        // RETURNS MULTIPLE 'User' OBJECTS            
    }

}

class User extends Zend_Db_Table_Row_Abstract {

    public function setPassword() {
        // SET THE PASSWORD FOR A SINGLE ROW
    }

}

/* CONTROLLER */
public function setPasswordAction() {

    /* GET YOUR PARAMS */

    $users = new Users();

    $user = $users->getById($id);

    $user->setPassword($password);

    $user->save();
}

There are numerous ways to approach this. Don't think this is the only one, but I try to follow the intent of the ZF's design. (Here are more of my thoughts and links on the subject.) This approach does get a little class heavy, but I feel it keeps the controllers focused on handling input and coordinating with the view; leaving the model to do the application specific work.

Solution 2

I worked for Zend and did quite a bit of work on the Zend_Db_Table component.

Zend Framework doesn't give a lot of guidance on the concept of a "Model" with respect to the Domain Model pattern. There's no base class for a Model because the Model encapsulates some part of business logic specific to your application. I wrote a blog about this subject in more detail.

Persistence to a database should be an internal implementation detail of a Model. The Model typically uses one or more Table. It's a common but improper object-oriented design to consider a Model as an extension of a Table. In other words, we should say Model HAS-A Table -- not Model IS-A Table.

This is an example of IS-A:

class MyModel extends Zend_Db_Table_Abstract
{
} 

This is an example of HAS-A:

class MyModel // extends nothing
{
    protected $some_table;
}

In a real domain model, you would use $some_table in the methods of MyModel.

You can also read Martin Fowler's take on the Domain Model design pattern, and his description of the Anemic Domain Model antipattern, which is how many developers unfortunately approach OO programming.

Solution 3

I've been doing some research on Models for ZF and came across an interesting series of articles by Matthew Weier O'Phinney which are well worth checking out:

• Using Zend_Form in your Models
• Applying ACLs to Models
• Model Infrastructure

It's not "production code" and a lot is left to the imagination, but it's a good read and has helped me quite a bit.

Solution 4

Don't ever use Zend_Db_Table as your model. It just gets you into trouble. Either you write your own model classes which use Zend_Db_Table to talk to your database or you can read my blog post here for a hack that allows you to somewhat combine the "Model" class and Zend_Db_Table.

The main thing to not is that when you use Zend_Db_Table directly in your controllers you end up doing the same things in multiple places. If you have to make a change to some of that logic, you have to make a change in multiple places. Not good. My first professional project was done like this because I was the one in the company who had to learn how to use ZF and it's a total mess now.

I also tend to write helper functions into my classes for sophisticated fetches. Somthing like $table->doNameFetchAll() or $table->doOrderFetchAll().

Solution 5

A model has nothing to do with the database. What if I am fetching data from an RSS feed or a SOAP service or reading files from the FS?

I put all these kinds of things in models. In that case, my model class might not extend anything. I'm about to write a model that uses methods of other models.

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