[RESOLVED] Objects & Inheritance

dougal85

Need a little advice.

It makes sense to me that I would have a user class and an admin clas.

The admin class extends user... so it has all the functionality plus the admin functions.

However, When populating the object with the data from the database... say i have a function called getUserByID()... this gets the user data. However, I don't know if the user is going to be an admin until after this. So i cant explicitly make a new admin.

So how would i call the right class?

bretticus

Is there the possibility that an admin and a user are basicaly the same "animal" and instead of a whole new class, you just need one user class that handles roles?

dougal85

hmm... i guess your right.

so lets say i have a function... um... deleteuser that admins can only use. Where would you place that and how would you restrict access to only the admin?

Thanks bretticus btw, your being loads of help

Shrike

Why won't you know if it is an admin user? How would you distinguish between the two in the database? Surely that distinction is enough to allow you to decide which class should be used. You might want to consider an abstact class with methods common to all users, and then User and AdminUser subclasses.

However to me that seems like confusing responsibilities. I would put 'admin functions' in a class of their own, or perhaps a few classes. Maybe an AdminUser manages regular Users, so I'd see the need for a UserManager class. But the distinction between Admin and Regular user would only exist in the database.

class User
{
  private $status;
  public function findUserById()
  {}
  public function isAdmin()
  {
    return $this->status == 1 ? true : false;
  }
}
class UserManager
{
  public function deleteUser( $userid )
  {}
}
$user = new User();
$user->findUserById( 'admin' );
if( $user->isAdmin() )
{
  $manager = new UserManager();
  $manager->deleteUser( 'fred' );
}

Edit: got in there before me 🙂

bretticus

dougal85 wrote:
so lets say i have a function... um... deleteuser that admins can only use. Where would you place that and how would you restrict access to only the admin?

Well, I certainly don't want to hamper your creativity or ingenuity so I'll just explain how I do this.

I have a roles table in my database where I define user roles. They can be anything from generics like 'admin', 'user' to even actions like 'report printer', 'user creator', etc. Of course these are two different approaches as the first defines the user and the second defines what any user can do. I prefer the second because it's so easy to use logic like

if ($this->userInRole('report printer')) do something...

dougal85

ah i see... that way makes sense.

I was thinking it would be hard because if you had two classes

user
admin

and admin extends user then you wouldnt know what one you were creating until after you created it. new user or new admin.

Does that make sense? lol.

I think i get you now... thats cool. Thanks to both of you 🙂 I'll go and give it a shot.

I may one day get this oop 100% sorted in my head

dougal85

uuuughhhhhhh i didn't see the post by bretticus..

I didn't understand your explanation there. Well, i understood half... you can either create the user and define the roles or you can create the roles and define if the user can do them.
That makes sense, but i don't understand how the implementation would work.

I get the feeling i'm missing something really simple and waiting for that lightbulb to turn on!

bretticus

dougal85 wrote:
I didn't understand your explanation there. Well, i understood half... you can either create the user and define the roles or you can create the roles and define if the user can do them.
That makes sense, but i don't understand how the implementation would work.

okay, when any user logs in, I query some joined tables: user->user-roles->roles. the user-roles table might look like...

userid|roleid

1 |1

etc, etc...

I store the role names as an array in a session variable. So a session variable for a given user might have "create reports" or "print reports", etc. Of course this is all internal to the user class. So when calling some method: "DoSomething()" in PHP within the class, for example. I can check if the currently authenticated user has that role. Make sense?

dougal85

I see, I understand that better. Thanks.

I'm starting up a project atm, its only personal so its kinda experimental. I'll be in touch if (or when) i get stuck! since you seem to know what your talking about! haha

Cheers again