php - 由父母和孩子共同构建

Question

I want to make such thing in php: I want to have the parent class named "item", and a bunch of child classes like "sword", "armor" etc. I can call simply:

$some_sword = new sword($id) ;

But I also want to do sth like this:

$some_sword = new item("sword",$id) ;

And I want both codes do he same effect. $some_sword must be the same class in both ways!

Answer 1

the new keyword will always return an instance of the class in question. however you can use a static method in the parent to return child class object (or any objects for that matter).

class Item
{
    public function __construct($id)
    {
        //Whatever
    }

    /**
     * Gets the object requested and passes the ID
     *
     * @param string object to return
     * @param integer id
     * @return object
     */
    public static function get($itemtype, $id)
    {
        $classname = ucfirst($itemtype);
        return new $classname($id);
    }
}

class Sword extends Item
{
    public function __construct($id)
    {
        //Whatever
    }
}

class Armor extends Item
{
    public function __construct($id)
    {
        //Whatever
    }
}

// Client Code
$some_sword = Item::get('sword', 1);
$some_armor = Item::get('armor', 2);