php面向对象编程 设计模式 - tianxintian22

面向对象编程的基本原则：

• 单一职责：一个类，只需要做好一件事
• 开放封闭：一个类，应该是可扩展的，而不是可修改的
• 依赖倒置：一个类，不应该强依赖另一个类。每个类对应另外一个类都是可替换的
• 配置化：尽可能地使用配置，而不是硬编码
• 面向接口编程：只需要关心接口，不需要关心实现

 1、设置类的属性

<span style="color: #0000ff;">class</span><span style="color: #000000;"> ShopProduct {
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$title</span> = 'default product'<span style="color: #000000;">;
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$producterMainName</span> = 'main name'<span style="color: #000000;">;
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$producterFirstName</span> = 'first name'<span style="color: #000000;">;
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$price</span> = 0<span style="color: #000000;">;
}

</span><span style="color: #800080;">$product1</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> ShopProduct();

</span><span style="color: #008000;">//</span><span style="color: #008000;">设置属性</span>
<span style="color: #800080;">$product1</span>->title = "My Antonia"<span style="color: #000000;">;
</span><span style="color: #800080;">$product1</span>->producterFirstName = "Cather"<span style="color: #000000;">;
</span><span style="color: #800080;">$product1</span>->producterMainName = "Willa"<span style="color: #000000;">;
</span><span style="color: #800080;">$product1</span>->price = 5.99<span style="color: #000000;">;

</span><span style="color: #008000;">//</span><span style="color: #008000;">访问</span>
<span style="color: #0000ff;">echo</span> 'author: '.<span style="color: #800080;">$product1</span>->producterFirstName.' '.<span style="color: #800080;">$product1</span>->producterMainName;

用以上方法设置属性值会有很多问题：

第一：PHP允许动态设置属性，如果拼错或忘记属性名时并不会得到警告。例如错误地把

<span style="color: #800080;">$product1</span>->producterMainName = "Willa";

写作

<span style="color: #800080;">$product1</span>->producterSecondName = "Willa";

，当我们输出作者名字的时候，会有意想不到的结果。

第二：类太过松散，我们没有强制设置标题、价格或者产品名称，客户端代码可以确定的是这些属性存在，但是面对的可能是默认值也可能不是，理想情况下，我们希望实例化ShopProduct对象时设置有意义的属性值。

第三：不得不重复做一些经常做的事，比如多次需要完整输出作者的名字，就要重复使用

<span style="color: #0000ff;">echo</span> 'author: '.<span style="color: #800080;">$product1</span>->producterFirstName.' '.<span style="color: #800080;">$product1</span>->producterMainName;

改进后的：

2、使用方法

<span style="color: #0000ff;">class</span><span style="color: #000000;"> ShopProduct {
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$title</span><span style="color: #000000;">;
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$producterMainName</span><span style="color: #000000;">;
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$producterFirstName</span><span style="color: #000000;">;
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$price</span> = 0<span style="color: #000000;">;
<br>　　 <span style="color: #008000;">//设置默认值，$this伪变量把类指向一个对象实例，$this可以理解为当前实例
    </span></span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span> __construct(<span style="color: #800080;">$title</span>, <span style="color: #800080;">$producterMainName</span>, <span style="color: #800080;">$producterFirstName</span>, <span style="color: #800080;">$price</span><span style="color: #000000;">){
        </span><span style="color: #800080;">$this</span>->title = <span style="color: #800080;">$title</span><span style="color: #000000;">;
        </span><span style="color: #800080;">$this</span>->producterMainName = <span style="color: #800080;">$producterMainName</span><span style="color: #000000;">;
        </span><span style="color: #800080;">$this</span>->producterFirstName = <span style="color: #800080;">$producterFirstName</span><span style="color: #000000;">;
        </span><span style="color: #800080;">$this</span>->price = <span style="color: #800080;">$price</span><span style="color: #000000;">;
    }
　　 <span style="color: #008000;">//获取作者名
    </span></span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> getProducter(){
        </span><span style="color: #0000ff;">return</span> <span style="color: #800080;">$this</span>->producterFirstName.' '.<span style="color: #800080;">$this</span>-><span style="color: #000000;">producterMainName;
    }

}

</span><span style="color: #800080;">$product1</span> = <span style="color: #0000ff;">new</span> ShopProduct('My Antonia', 'Willa', 'Cather', 5.99<span style="color: #000000;">);

</span><span style="color: #008000;">//</span><span style="color: #008000;">访问</span>
<span style="color: #0000ff;">echo</span> 'author: '.<span style="color: #800080;">$product1</span>->getProducter();

 3、使用AccessArray实现配置文件的加载

ArrayAccess 是提供像访问数组一样访问对象的能力的接口。

Config.php

<span style="color: #000000;">php
namespace Baobab;

</span><span style="color: #0000ff;">class</span> Config <span style="color: #0000ff;">implements</span><span style="color: #000000;"> \ArrayAccess{

    </span><span style="color: #0000ff;">protected</span> <span style="color: #800080;">$path</span><span style="color: #000000;">;
    </span><span style="color: #0000ff;">protected</span> <span style="color: #800080;">$configs</span> = <span style="color: #0000ff;">array</span><span style="color: #000000;">();
    </span><span style="color: #008000;">/*</span><span style="color: #008000;">*
     * @param $path 配置文件所在的文件系统目录
     </span><span style="color: #008000;">*/</span>
    <span style="color: #0000ff;">function</span> __construct(<span style="color: #800080;">$path</span><span style="color: #000000;">){
        </span><span style="color: #800080;">$this</span>->path = <span style="color: #800080;">$path</span><span style="color: #000000;">;
    }

    </span><span style="color: #0000ff;">function</span> offsetGet(<span style="color: #800080;">$key</span><span style="color: #000000;">){
        </span><span style="color: #0000ff;">if</span> (<span style="color: #0000ff;">empty</span>(<span style="color: #800080;">$this</span>->configs[<span style="color: #800080;">$key</span><span style="color: #000000;">])){
            </span><span style="color: #800080;">$file_path</span> = <span style="color: #800080;">$this</span>->path.'/'.<span style="color: #800080;">$key</span>.'.php'<span style="color: #000000;">;
            </span><span style="color: #800080;">$config</span> = <span style="color: #0000ff;">require</span> <span style="color: #800080;">$file_path</span><span style="color: #000000;">;
            </span><span style="color: #800080;">$this</span>->configs[<span style="color: #800080;">$key</span>] = <span style="color: #800080;">$config</span><span style="color: #000000;">;
        }
        </span><span style="color: #0000ff;">return</span><span style="color: #800080;">$this</span>->configs[<span style="color: #800080;">$key</span><span style="color: #000000;">];
    }

    </span><span style="color: #0000ff;">function</span> offsetSet(<span style="color: #800080;">$key</span>, <span style="color: #800080;">$value</span><span style="color: #000000;">){
        </span><span style="color: #0000ff;">throw</span> <span style="color: #0000ff;">new</span> \<span style="color: #0000ff;">Exception</span>("can't write config file"<span style="color: #000000;">);
    }

    </span><span style="color: #0000ff;">function</span> offsetExists(<span style="color: #800080;">$key</span><span style="color: #000000;">){
        </span><span style="color: #0000ff;">return</span> <span style="color: #0000ff;">isset</span>(<span style="color: #800080;">$this</span>->configs[<span style="color: #800080;">$key</span><span style="color: #000000;">]);
    }

    </span><span style="color: #0000ff;">function</span> offsetUnset(<span style="color: #800080;">$key</span><span style="color: #000000;">){
        </span><span style="color: #0000ff;">unset</span>(<span style="color: #800080;">$this</span>->configs[<span style="color: #800080;">$key</span><span style="color: #000000;">]);
    }
}</span>

/Configs/database.php

<span style="color: #000000;">php
</span><span style="color: #800080;">$config</span> = <span style="color: #0000ff;">array</span><span style="color: #000000;">(
    </span>'master' => <span style="color: #0000ff;">array</span><span style="color: #000000;">(
        </span>'type' => 'MySQL',
        'host' => '127.0.0.1',
        'user' => 'root',
        'password' => 'root',
        'dbname' => 'test'<span style="color: #000000;">
    )
);

</span><span style="color: #0000ff;">return</span> <span style="color: #800080;">$config</span>;

index.php

<span style="color: #800080;"><span style="font-style: italic;">define<span>(<span style="color: #008000; font-weight: bold;">'BASEDIR'<span>,<span style="color: #660e7a; font-weight: bold; font-style: italic;">__DIR__<span>);</span></span></span></span></span></span><br>$config</span> = <span style="color: #0000ff;">new</span> \Baobab\Config(BASEDIR.'/Configs'<span style="color: #000000;">);
</span><span style="color: #008000;">//</span><span style="color: #008000;">从文件系统加载一个配置文件Configs/database.php</span>
<span style="color: #008080;">print_r</span>(<span style="color: #800080;">$config</span>['database']);