[RESOLVED] Classes Usage Question

aaron_karp

Hey, I'm finally going to start using OOP

:: Insert member jeers and taunts ::

Ok, now that that's aside, I was hoping you guys could help me plan out a class a little bit, and let me know if I even need a class for this.

My site has a database of users. These users are linked to articles that they've submitted. I expect that I'll need functions to retrieve all the articles that a certain user has written. I'll also need functions to change and retrieve a user's personal information, etc. Then, I'll need methods for creating new articles, editing existing articles, etc.

Do I just create a User class with methods like getAllArticles()? And then do:

$activeUser = new User();
$allNotes = $activeUser->getAllArticles();

Is that right? The syntax isn't really my worry. I'm just concerned about whether or not I'm using classes correctly.

Shrike

You should think in terms of responsibilities as well as functionality. A user object probably doesn't have the responsibility of retreiving articles, it's concerned with users. In this way the code might look more like this.

$username = 'Me';
$user = UserFinder::findUser( $username );
$articles = ArticleFinder::findrArticles($user->getUserId() );
while( $article = $articles->next() )
{
  echo $article->getTitle() . ' ' . $article->getAuthor();
}

UserFinder and ArticleFinder are known as data access objects (classes rather than objects in this case). They're responsibility is translating database rows into objects. User and Article are known as value objects, with the responsibility of holding and manipulating data.

The while loop also implies another particular pattern of OO design, the Iterator. It provides a common way of handling sets of data (sets of articles in this case). In fact Iterator is such a useful pattern that many languages (PHP 5, Java, Ruby to name a few) provide Iterators as part of the language.

Some food for thought.

aaron_karp

Perfect! This is exactly what I was looking for (data access objects). I knew it didn't make sense to create a new object. But this still lets me compartmentalize the methods in a Class, which is what I was wanted to do.

Thanks.