04-状态模式.php

<?php

declare(strict_types=1);

/*
 * This file is modified from `xiaohuangniu/26`.
 *
 * @see https://github.com/xiaohuangniu/26
 */

header('Content-type: text/html; charset=utf-8');

/**
 * 派生出相关的接口状态
 */
interface IState
{
    public function WriteCode($Work);
}

/**
 * 春季.
 */
class AState implements IState
{
    public function WriteCode($Work)
    {
        if ($Work->hour == '春') {
            echo '春季，要下雨啦！'.PHP_EOL;
        } else {
            // 调用回调方法，去访问夏季方法
            $Work->SetState(new BState());
            $Work->WriteCode();
        }
    }
}

/**
 * 夏季.
 */
class BState implements IState
{
    public function WriteCode($Work)
    {
        if ($Work->hour == '夏') {
            echo '夏季，好热额！'.PHP_EOL;
        } else {
            // 调用回调方法，去访问秋季方法
            $Work->SetState(new CState());
            $Work->WriteCode();
        }
    }
}

/**
 * 秋季.
 */
class CState implements IState
{
    public function WriteCode($Work)
    {
        if ($Work->hour == '秋') {
            echo '秋季，恋爱的季节！'.PHP_EOL;
        } else {
            // 调用回调方法，去访问冬季方法
            $Work->SetState(new DState());
            $Work->WriteCode();
        }
    }
}

/**
 * 冬季.
 */
class DState implements IState
{
    public function WriteCode($Work)
    {
        if ($Work->hour == '冬') {
            echo '冬季，浪漫的季节！'.PHP_EOL;
        } else {
            echo '你不是地球人！'.PHP_EOL;
        }
    }
}

/**
 * 处理季节筛选.
 */
class Work
{
    public $hour; // 季节成员

    public $isDone;

    private $current; // 季节对象实例

    /**
     * 默认选择第一个筛选项.
     */
    public function __construct()
    {
        $this->current = new AState();
    }

    /**
     * 当筛选不正确时，调用该方法继续向下筛选.
     * @param  mixed  $S
     */
    public function SetState($S)
    {
        $this->current = $S;
    }

    /**
     * 调用这个方法，使用筛选.
     */
    public function WriteCode()
    {
        $this->current->WriteCode($this);
    }
}

// 实例DEMO
$obj = new Work();
$obj->hour = '春';
$obj->WriteCode();
$obj->hour = '夏';
$obj->WriteCode();
$obj->hour = '秋';
$obj->WriteCode();
$obj->hour = '冬';
$obj->WriteCode();
$obj->hour = '小黄牛';
$obj->WriteCode();