S7:享元模式 Flyweight

运用共享技术有效的支持大量细粒度的对象.

应用场景:

A.减少对相同对象的重复创建

UML:

　　

示例代码:
如果在工厂中,有用户,我们就直接调用,没有用户,我们就获取.减少对同一uid的user对象的重复创建.

interface FlyWeight
{
    public function __construct($uid);
}

class User implements FlyWeight
{
    protected $uid;
    public function __construct($uid)
    {
        $this->uid = $uid;
    }

    public function __toString()
    {
        return 'uid' . $this->uid . PHP_EOL;
    }
}

class Factory
{
    public static $users = array();

    public static function getUser($uid)
    {
        if (! array_key_exists($uid, self::$users)) {
            self::$users[$uid] = new User($uid);
        }

        return self::$users[$uid];
    }
}

$user1 = Factory::getUser(1);
$user2 = Factory::getUser(2);

$user3 = new User(3);

echo($user1);
echo($user2);
echo($user3);