PHP设计模式之装饰者模式

装饰者模式(Decorator Pattern)

• 装饰者模式允许向一个现有的对象添加新的功能，同时又不改变其结构
• 如果要修改并添加一个类中额外的功能，传统的编程模式需要写一个子类继承它，并重新实现类的方法
• 使用装饰者模式，仅需在运行时添加一个装饰器对象即可实现，可以实现最大的灵活性

IDecorator接口

interface IDecorator
{
    public function beforeDo();
    public function afterDo();
}

需要改进的类

<?php
namespace core;

class DecoratorPattern
{
    public $name;
    protected $decorators = [];  // 存放装饰器

    public function __construct($name)
    {
        $this->name = $name;
    }
    // 增加装饰器
    public function addDecorator(IDecorator $decorator)
    {
        $this->decorators[] = $decorator;
    }

    public function beforeDo()
    {
        foreach ($this->decorators as $decorator) {
            $decorator->beforeDo();
        }
    }

    public function afterDo()
    {
        // 反转数组，先进后出
        $decorators = array_reverse($this->decorators);
        foreach ($decorators as $decorator) {
            $decorator->afterDo();
        }
    }

    public function echoName()
    {
        $this->beforeDo();
        echo $this->name;
        $this->afterDo();
    }
}

颜色装饰器类

<?php
namespace core;

class ColorDecorator implements IDecorator
{
    protected $color;

    public function __construct($color = 'red')
    {
        $this->color = $color;
    }

    public function beforeDo()
    {
        echo "<p>颜色即将更改为：{$this->color}</p>";
        echo "<div style='color: {$this->color}'>";
    }

    public function afterDo()
    {
        echo "</div>";
        echo "<p>颜色已更改为：{$this->color}</p>";
    }
}

实现

$descrator1 = new \core\DecoratorPattern("小明");
$descrator1->addDecorator(new \core\ColorDecorator('green'));   // 添加绿色装饰者
$descrator1->addDecorator(new \core\ColorDecorator('red'));     // 添加红色装饰者
$descrator1->addDecorator(new \core\ColorDecorator('blue'));    // 添加蓝色装饰者
$descrator1->echoName();

结果