Advancing My OOP Skills :)

[seventheyejosh]

So I've been trying to furthor my OOP knowledge, so I've been trawling through the php.net manual as well as countless online tutorials. I've finally clicked about visibility, but I have a question about extends.

 

What is a real world example when you would do class a extends class b?

 

And has anyone ever used the final decleration?

 

Thanks a lot

 

[KevinM1]

So I've been trying to furthor my OOP knowledge, so I've been trawling through the php.net manual as well as countless online tutorials. I've finally clicked about visibility, but I have a question about extends.

 

What is a real world example when you would do class a extends class b?

 

And has anyone ever used the final decleration?

 

Thanks a lot

 

 

Extending a class is used often in the Command pattern.

 

abstract class Command
{
   private $request;

   public function __construct(Request $request)
   {
      $this->request = $request;
   }

   public abstract function execute();
}

class Login_Command extends Command
{
   public function execute()
   {
      //assume we already have a db connection
      //request validation goes here...if valid $user = $this->request->getValue('user') and $pass = md5($this->request->getValue('pass'))

      $result = mysql_query("SELECT * FROM users WHERE username = $user AND pass = $pass");

      if (mysql_num_rows($result) == 1) { /* success */ }
      else { /* error */ }
   }
}

 

Rough sketch, but you should get the idea.

[corbin]

final is really not used all that often.

 

 

The only use of final is to make sure a method cannot be over ridden if the class is extended.  (Or, in the case of a final class, to make sure that the class can't be extended.)

 

 

Off the top of my head I can't think of an example situation >.<.

 

(Which probably doesn't help you much since I'm sure you knew what the final keyword does.)