PHP - unique attribute for objects of a class

Question

I have this class

class MyClass{
    private $id;
    private $name;
    public function __construct ($id, $name){
        $this->name = $name;
    }
}

$ob1 = new MyClass(1, 'earth');
$ob2 = new MyClass(2, 'sky');
$ob3 = new MyClass(3, 'ocean');

I want that my objects $ob1, $ob2 and $ob3 have a different attribute $id. For example when i make this :

$ob4 = new MyClass(3, 'wood');

The code denies me to create the object

Thanks

No there is no database. it is just variables in memory.

medzbakh
– medzbakh

2016-01-16 20:21:11 +00:00
Commented Jan 16, 2016 at 20:21 — medzbakh
– medzbakh, Commented Jan 16, 2016 at 20:21

deceze · Accepted Answer · 2016-01-16 15:17:37Z

3

You need to keep track of the ids in a static class property:

class MyClass {
    static private $ids = [];

    public function __construct($id) {
        if (in_array($id, self::$ids)) {
            throw new Exception("Object with id $id already constructed");
        }
        self::$ids[] = $id;
    }
}

Having said this, I would question the usefulness of this. It just sounds like a recipe for problems. You should keep track of unique data as part of some business logic and database interaction, probably not as something enforced on a language level.

answered Jan 16, 2016 at 15:17

deceze♦

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1 Comment

GolezTrol Over a year ago

Can be handy as a repository. You could even add a static function getInstance($id) that returns an object with that id from the static array, or constructs a new one if it doesn't exist yet. But whether this is really the best implementation for it.. Mwah..

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