设计模式之装饰模式

将所有功能建立在继承体系上会导致系统中的类爆炸式的增多。更糟糕的是当你尝试继承数上不同的分支做相似的修改时，代码会产生重复。

装饰模式是解决此类问题很好的办法。代码如下

bstract class tile{

abstract function getWealthFactor();

}

class Plains extends tile(){

private $wealthFactor = 2;

function getWealthFactor(){

return $this->wealthFactor;

}

}

//重点代码

abstract class tileDecorator extends tile(){

protected $tile;

function __construct($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;

}

}

$Plains = new Plains();

$Plains->getWealthFactor; //2

$tile = new diamondDecorator(new Plains());

$tile->getWealthFactor();//4

$tile = new pollutionDecorator(new diamondDecorator(new Plains()))

$tile->getWealthFactor();//0

若不用装饰模式，那么则既有污染又有钻石的情况又需要增加一个新类来继承。

若如代码所示，加一个区域装饰器tileDecorator，代码就可以灵活组合，降低耦合。需要的类大大减少，组建系统也更加的灵活。可以更容易的增加若干新的装饰器来满足各种复杂的情况。