Zend Framework - Database Table Singleton

Question

I have found myself doing this in my code to 'cache' the work done when instantiating my Zend_Db_Table models:

if (Zend_Registry::isRegistered('x_table')) {
    $x_table = Zend_Registry::get('x_table');
} else {
    $x_table = new Default_Model_DbTable_X;
    Zend_Registry::set('x_table', $x_table);
}

It bothered me that this method isn't very DRY and it dawned on me today that a singleton pattern would probably be a better way to do this. Problem is, I've never written a singleton class. When I did some web searches, I found some offhand comments about Zend_Db_Table singletons, but no real examples.

I already have meta-data caching configured.

How do I make my Zend_Db_Table models singletons?
Are there pitfalls or downsides?

Edit: My reason for thinking a singleton was the answer is that I thought I could simply have the following calls in my code $x_table = new Default_Model_DbTable_X; and the single instance would be returned if it existed. If this is possible, I would prefer that solution.

What are you doing in your code that you need to instantiate multiple instances of the same table in the same request? — Gordon
– Gordon, Commented Apr 14, 2010 at 22:14
I am building a CMS and the tables contain content. Content blocks can be put into a page, and the page may have more than one of the same type of block in it. Thanks for the reference! — Sonny
– Sonny, Commented Apr 14, 2010 at 22:56
you're welcome, but I still don't get why you need multiple instances of the same table instead of just passing around the first instance and doing multiple queries on it. — Gordon
– Gordon, Commented Apr 15, 2010 at 7:17
@Gordon - Sorry, I didn't answer your question correctly. I don't need multiple instances, that's what my code above is trying to mitigate. I (check for|store) the instance in the registry, which may or may not be there. My post is basically asking for a better way. — Sonny
– Sonny, Commented Apr 15, 2010 at 14:36

timdev · Accepted Answer · 2010-04-14 22:34:47Z

3

Why not just manage the DbTables in some sensible place? If there's no sensible place, create a DbTableManager class. Something like:

<?PHP
class DbTableMgr {

  protected $_tables;

  public function getTable($classname){
    if ( empty($this->_tables[$name]) ){
      //assuming some things about class names for the sake of brevity elsewhere...
      $classname = 'Default_Model_DbTable_',ucfirst(strtolower($classname));

      $this->_tables[$name] = new $classname; 
    }
    return $this->_tables[$name];  
  }
}

Initialize the manager in your bootstrap and stick it in the registry.

Then:

<?PHP
//in a galaxy far, far, away
$dbtFoo = Zend_Registry::get('dbtMgr')->getTable('Foo');

So, you lazy-load the dbTable objects, and enforce a singleton-like behavior.

You could make the above static in various ways, if you wanted to.

answered Apr 14, 2010 at 22:34

timdev

63.1k6 gold badges86 silver badges93 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Sonny Over a year ago

Your Zend_Registry method looks good, but I'm intrigued by what you meant by "sensible place". It sounds like you're implying that the Zend_Registry is a second-best solution.

timdev Over a year ago

Zend_Registry is fine for this kind of thing. I just meant that, depending on the application design, there might be a more sensible place to implement the dbTableManager stuff. But if you're not sure, there's nothing wrong with just making a class like I've shown, and sticking that into the registry while bootstrapping your database stuff.

SoWhat Over a year ago

okay this is an old question but m curious. Why not just make it a signleton. If nothing else it adds convinience. UserTable::getInstance()->getUsers()

timdev Over a year ago

@Somesh Mukherjee - You could do that too, but in that case you'd need to add another layer to your class hierarchy to provide the singleton behavior for all *Table classes. Zend_Registry is already there, and accomplishes essentially the same thing.

SoWhat Over a year ago

okay that is true. but i still think that's how Zend Tables should have been. The singeton pattern makes more sense than having a new object

Collectives™ on Stack Overflow

Zend Framework - Database Table Singleton

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related