PHP 面向对象编程和设计模式 (3)_PHP教程

<span>class</span><span> ClassName
{

    </span><span>public</span> <span>static</span> <span>$_instance</span><span>;
    
    </span><span>private</span> <span>function</span><span> __construct()
    {
        </span><span>#</span><span> code...</span>
<span>    }

    </span><span>private</span> <span>function</span><span> __clone()
    {
        </span><span>#</span><span> empty</span>
<span>    }

    </span><span>public</span> <span>static</span> <span>function</span><span> GetInstance()
    {
        </span><span>if</span>(!(self::<span>$_instance</span><span> instanceof self))
        {
            self</span>::<span>$_instance</span> = <span>new</span><span> self();
        }
        </span><span>return</span> self::<span>$_instance</span><span>;
    }

    </span><span>public</span> <span>function</span><span> SayHi()
    {
        </span><span>echo</span> "Hi boy!"<span>;
    }
}

</span><span>$App</span>= ClassName::<span>GetInstance();
</span><span>$App</span>-><span>SayHi();

</span><span>/*</span><span>*
 *
 * Output
 *
 * Hi boy! 
 *
 </span><span>*/</span>

<span>interface</span><span> ProductInterface
{
    </span><span>public</span> <span>function</span><span> showProductInfo();
}

</span><span>class</span> ProductA <span>implements</span><span> ProductInterface
{
    </span><span>function</span><span> showProductInfo()
    {
        </span><span>echo</span> 'This is product A.'<span>;
    }
}
</span><span>class</span> ProductB <span>implements</span><span> ProductInterface
{
    </span><span>function</span><span> showProductInfo()
    {
        </span><span>echo</span> 'This is product B.'<span>;
    }
}

</span><span>class</span><span> ProductFactory
{
    </span><span>public</span> <span>static</span> <span>function</span> factory(<span>$ProductType</span><span>)
    {        
        </span><span>$ProductType</span> = 'Product' . <span>strtoupper</span>(<span>$ProductType</span><span>);
        </span><span>if</span>(<span>class_exists</span>(<span>$ProductType</span><span>))
        {
            </span><span>return</span> <span>new</span> <span>$ProductType</span><span>();
        }
        </span><span>else</span><span>
        {
            </span><span>throw</span> <span>new</span> <span>Exception</span>("Error Processing Request", 1<span>);
            
        }
        
    }
}
//这里需要一个产品型号为 A 的对象
</span><span>$x</span> = ProductFactory::factory('A'<span>);
</span><span>$x</span> -><span> showProductInfo();
<br />//这里需要一个产品型号为 B 的对象
</span><span>$o</span> = ProductFactory::factory('B'<span>);
</span><span>$o</span> -><span> showProductInfo();<br /><br />//都可以调用showProductInfo方法，因为都实现了接口 ProductInterface.
</span>?>