php设计模式 State (状态模式)

/**
* 状态模式
*
* 允许一个对象在其内部状态改变时改变它的行为,对象看起来似乎修改了它所属的类
*
*/
interface State
{
public function handle($state);
public function display();
}
class Context
{
private $_state = null;
public function __construct($state)
{
$this->setState($state);
}
public function setState($state)
{
$this->_state = $state;
}
public function request()
{
$this->_state->display();
$this->_state->handle($this);
}
}
class StateA implements State
{
public function handle($context)
{
$context->setState(new StateB());
}
public function display()
{
echo "state A
";
}
}
class StateB implements State
{
public function handle($context)
{
$context->setState(new StateC());
}
public function display()
{
echo "state B
";
}
}
class StateC implements State
{
public function handle($context)
{
$context->setState(new StateA());
}
public function display()
{
echo "state C
";
}
}
// 实例化一下
$objContext = new Context(new StateB());
$objContext->request();
$objContext->request();
$objContext->request();
$objContext->request();
$objContext->request();