Decorator模式

<?php
/**
 * 装饰者模式
 * 装饰者以横向增长的方式扩展类的功能，
 * 而不是以继承的方式纵向扩展类的功能，
 * 从而有效防止继承的子类爆炸式的增多。
 * 来自<<深入PHP，面向对象，模式与实践>>
 */

abstract class Tile {
    abstract function getWealthFactor();
}

class Plains extends Tile{
    private $wealthfactor = 2;
    
    public function getWealthFactor() {
        return $this->wealthfactor;
    }
}

//<--------------使用继承--------------->
class DiamondPlains extends Plains {
    function getWealthFactor() {
        return parent::getWealthFactor() + 2;
    }
}

class PollutedPlains extends Plains {
    function getWealthFactor() {
        return parent::getWealthFactor() - 4;
    }
}

//获取diamond和polluted的健康系数
$diamond = new DiamondDecorator();
$diamondHealth = $diamond->getWealthFactor();

$polluted = new PollutedPlains();
$pollutedHealth = $polluted->getWealthFactor();

//<--------------使用装饰者--------------->
//装饰者超类
class TileDecorator {
    protected $tile;
    //获取需要装饰的对象。
    function __construct(Tile $tile) {
        $this->tile = $tile;
    }
}

class DiamondDecorator extends TileDecorator{
    function getWealthFactor() {
        return $this->tile->getWealthFactor() + 2;
    }
}

class PollutionDecorator extends TileDecorator{
    function getWealthFactor() {
        return $this->tile->getWealthFactor() - 4;
    }
}

//获取diamond和polluted的健康系数
//获取diamond装饰的tile对象的健康系数
$diamond = new DiamondDecorator(new Tile);
$diamondHealth = $diamond->getWealthFactor();

//获取polluted装饰的tile对象的健康系数
$polluted = new PollutionDecorator(new Tile);
$pollutedHealth = $polluted->getWealthFactor();

?>