PHP design pattern - memo pattern_PHP tutorial

PHP Design Pattern - Memo Pattern

Memo mode, also called snapshot mode or Token mode, captures the internal state of an object and saves this state outside the object without breaking the closure. This allows you to later restore the object to its original saved state.

UML class diagram:

Character:

1. Initiator (GameRole): Responsible for creating a memo to record its own internal state at the current moment, and can use the memo to restore the internal state. The originator can decide which of its own internal states the memo stores as needed.

2. Memo (RoleStateSaveBox): Responsible for storing the internal state of the initiator object and preventing other objects other than the initiator from accessing the memo. Memos have two interfaces: the manager can only see the narrow interface of the memo, and he can only pass the memo to other objects. The initiator, however, sees the memo's wide interface, allowing it to access all the data it needs to return to the previous state.

3. Manager (GameRoleStateManager): Responsible for accessing memos and cannot access or operate the content.

Core code:

<!--?php
/**
 * Created by PhpStorm.
 * User: Jang
 * Date: 2015/6/10
 * Time: 9:49
 */

//游戏角色
class GameRole
{
    #region 游戏角色状态属性（生命力、攻击力、防御力）
    public $liveLevel;

    public $attackLevel;

    public $defenseLevel;
    #endregion

    //保存状态
    public function SaveState()
    {
        return (new RoleStateMemento($this--->liveLevel,$this->attackLevel,$this->defenseLevel));
    }

    //恢复状态
    public function RecoveryState(RoleStateMemento $_memento)
    {
        $this->liveLevel = $_memento->liveLevel;
        $this->attackLevel = $_memento->attackLevel;
        $this->defenseLevel = $_memento->defenseLevel;
    }

    //------------其他属性及操作--------------
    //获得初始状态
    public function GetInitState()
    {
        $this->defenseLevel = 100;
        $this->attackLevel = 100;
        $this->liveLevel = 100;
    }

    //状态显示
    public function StateDisplay()
    {
        echo 角色状态：
;
        echo 生命力：{$this->liveLevel}
;
        echo 攻击力：{$this->attackLevel}
;
        echo 防御力：{$this->defenseLevel}
;
    }

    //被攻击
    public function BeenAttack()
    {
        $this->liveLevel -= 9.5;
        if($this->liveLevel<=0)
        {
            $this->liveLevel = 0;
            echo 呃，该角色阵亡了！
;
            echo Game Over!
;
            return;
        }

        $this->attackLevel -= 1.1;
        if($this->attackLevel<=0)
        {
            $this->attackLevel = 0;
        }

        $this->defenseLevel -= 0.5;
        if($this->defenseLevel<=0)
        {
            $this->defenseLevel = 0;
        }
    }
    }

//角色状态存储箱类
class RoleStateMemento
{
    public $liveLevel;
    public $attackLevel;
    public $defenseLevel;

    public function RoleStateMemento($_ll,$_al,$_dl)
    {
        $this->liveLevel=$_ll;
        $this->attackLevel=$_al;
        $this->defenseLevel=$_dl;
    }
}

//游戏角色状态管理者类
class RoleStateManager
{
    public $memento;
}

Test code:

<!--?php
/**
 * Created by PhpStorm.
 * User: Jang
 * Date: 2015/6/10
 * Time: 10:02
 */

header(Content-Type:text/html;charset=utf-8);
//-------------------------备忘录模式------------------------
require_once ./Memento/Memento.php;

//开战前
$ufo = new GameRole();
$ufo--->GetInitState();
echo <span style="'color:#ff0000'">----------------开战前-----------------</span>
;
$ufo->StateDisplay();

//保存进度
$roleMan = new RoleStateManager();
$roleMan->memento = $ufo->SaveState();

echo <span style="'color:#ff0000'">----------------战斗中-----------------</span>
;
$num=1;
//大战Boss5个回合
for ($i = 0; $i <13;$i++ )
{
    echo -------------第{$num}回合-------------
;
    $ufo->BeenAttack();
    $ufo->StateDisplay();
    $num++;
    //角色阵亡
    if($ufo->liveLevel<=0)
    {
        break;
    }
}

echo <span style="'color:#ff0000'">----------------恢复状态-----------------</span>
;
//恢复之前状态
$ufo->RecoveryState($roleMan->memento);
$ufo->StateDisplay();

Advantages:

1. Sometimes some internal information of the initiator object must be stored outside the initiator object, but must be read by the initiator object itself. In this case, the memo mode can be used to transfer the complex internal information of the initiator to other objects. Objects are masked so that encapsulated boundaries are properly maintained.

2. This mode simplifies the initiating human. Initiators no longer need to manage and save versions of their internal states, and clients can manage the versions of these states they need.

Disadvantages:

1. If the status of the initiator role needs to be completely stored in the memo object, then the memo object will be very expensive in terms of resource consumption.

2. When the person in charge stores a memo, the person in charge may not know how much storage space this status will occupy, and thus cannot remind the user whether an operation is expensive.

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