/**
* 具体状态角色B
* 单例类
*/
class ConcreteStateB implements State {
/* 唯一的实例 */
private static $_instance = null;
private function __construct() {
}
/**
* 静态工厂方法，返还此类的唯一实例
*/
public static function getInstance() {
if (is_null(self:_instance)) {
self:_instance = new ConcreteStateB();
}
return self:_instance;
}
public function handle(Context $context) {
echo 'Concrete Sate B handle method
';
$context->setState(ConcreteStateA::getInstance());
}
}
/**
* 环境角色
*/
class Context {
private $_state;
/**
* 默认为StateA
*/
public function __construct() {
$this->_state = ConcreteStateA::getInstance();
}
public function setState(State $state) {
$this->_state = $state;
}
public function request() {
$this->_state->handle($this);
}
}
/**
* 客户端
*/
class Client {
/**
* Main program.
*/
public static function main() {
$context = new Context();
$context->request();
$context->request();
$context->request();
$context->request();
}
_instance)) {