设计模式学习笔记(6) - 状态模式

状态模式与策略模式很像，真的很像。

下面举个例子来说明，我们都知道银行经常将用户划分个三六九等，划分的方法很简单，就是用户的存款。下面用php代码来模拟下这个过程：

<?php
/**
 *  状态模式的例子
 *
 *  Copyright(c) 2012 by ustb80. All rights reserved
 *
 *  To contact the author write to {@link mailto:[email protected]}
 *
 * @author ustb80
 * @version $Id: State.php,v 1.0 2012-11-01
 * @package
 */

// ------------------------------------------------------------------------

$config = array('new'=>10, 'silver'=>10000, 'gold'=>999999999999);

/**
 * 状态抽象类
 *
 * @author ustb80
 */
abstract class State
{
    protected $client;
    protected $silver_limit = 10;
    protected $gold_limit = 10000;

    abstract function deposit($amount);// 存款
    abstract function withdraw($amount);// 取款

    protected function changeState()
    {
        global $config;
        if (!empty($config))
        {
            foreach ($config as $key => $val)
            {
                if ($this->client->balance < $val)
                {
                    $state_name = ucfirst($key)."State";
                    echo "亲，你已经成为{$key}卡用户\n";
                    $this->client->setState($this->client->$state_name);
                    break;
                }
            }
        }
    }
}

// 实现各种乱七八糟的状态

// 新用户
class NewState extends State
{
    public function __construct($client)
    {
        $this->client = $client;
    }

    public function deposit($amount)
    {
        $this->client->balance += $amount;
        $this->changeState();
    }

    public function withdraw($amount)
    {
        die("亲，你还没存钱呢就想着取钱呀，门儿都没有！\n");
    }
}

// 银卡用户
class SilverState extends State
{
    public function __construct($client)
    {
        $this->client = $client;
    }

    public function deposit($amount)
    {
        $this->client->balance += $amount;
        $this->changeState();
    }

    public function withdraw($amount)
    {
        if ($this->balance < $amount)
        {
            die("亲，余额不足\n");
        }

        $this->client->balance -= $amount;
        $this->changeState();
    }
}

// 金卡用户
class GoldState extends State
{
    public function __construct($client)
    {
        $this->client = $client;
    }

    public function deposit($amount)
    {
        $this->balance += $amount;
    }

    public function withdraw($amount)
    {
        if ($this->client->balance < $amount)
        {
            die("亲，余额不足\n");
        }

        $this->client->balance -= $amount;
        $this->changeState();
    }
}


// -------------------------------------------------------------

/**
 * 银行客户类
 *
 * @author ustb80
 */
class BankClient
{
    public $balance;
    private $state;
    public function __construct()
    {
        global $config;
        foreach ($config as $key => $val)
        {
            $method_name = ucfirst($key)."State";
            $this->$method_name = new $method_name($this);
        }

        // 初始化状态
        $this->state = $this->NewState;
    }
    /**
     * 存钱
     *
     * @param float $amount 存入金额
     */
    public function deposit($amount)
    {
        $this->state->deposit($amount);
    }

    /**
     * 取钱
     *
     * @param float $amount 取出金额
     */
    public function withdraw($amount)
    {
        $this->state->withdraw($amount);
    }

    /**
     * 变更状态
     *
     * @param object $state
     */
    public function setState($state)
    {
        $this->state = $state;
    }

    /**
     * 查看余额
     */
    public function getBalance()
    {
        return $this->balance;
    }
}

// 测试代码
$BankClient = new BankClient();
$BankClient->deposit(10000);
$BankClient->withdraw(5000);
$BankClient->deposit(100000);

// 查看余额
echo $BankClient->getBalance();

上面用了一个配置数组来动态创建对象实例。

输出结果：

亲，你已经成为gold卡用户
亲，你已经成为silver卡用户
亲，你已经成为gold卡用户
105000