备忘录模式

<?php
 
// 备忘录类
class Memento
{
    private $state;
 
    public function __construct(string $state)
    {
        $this->state = $state;
    }
 
    public function getState(): string
    {
        return $this->state;
    }
}
 
// 发起人类
class Originator
{
    private $state;
 
    public function setState(string $state): void
    {
        echo "发起人: 设置状态为 $state\n";
        $this->state = $state;
    }
 
    public function saveStateToMemento(): Memento
    {
        echo "发起人: 保存状态到备忘录\n";
        return new Memento($this->state);
    }
 
    public function getStateFromMemento(Memento $memento): void
    {
        $this->state = $memento->getState();
        echo "发起人: 从备忘录恢复状态为 $this->state\n";
    }
}
 
// 看护者类
class Caretaker
{
    private $mementoList = [];
 
    public function add(Memento $state): void
    {
        $this->mementoList[] = $state;
    }
 
    public function get(int $index): Memento
    {
        return $this->mementoList[$index];
    }
}
 
// 客户端代码
$originator = new Originator();
$caretaker = new Caretaker();
 
$originator->setState("状态1");
$originator->setState("状态2");
$caretaker->add($originator->saveStateToMemento());
 
$originator->setState("状态3");
$caretaker->add($originator->saveStateToMemento());
 
$originator->setState("状态4");
 
echo "\n当前状态: " . $originator->saveStateToMemento()->getState() . "\n";
 
$originator->getStateFromMemento($caretaker->get(0));
echo "\n恢复到第一个保存的状态: " . $originator->saveStateToMemento()->getState() . "\n";
 
$originator->getStateFromMemento($caretaker->get(1));
echo "\n恢复到第二个保存的状态: " . $originator->saveStateToMemento()->getState() . "\n";