我一般不太习惯设计模式，也从未使用过装饰器。我想要一个可以根据上下文具有不同行为的对象。这些行为在不同的类中定义。我猜装饰器可以解决问题。但我需要每个装饰器都可以访问相同的属性，并首先调用子方法，就像继承一样。所以在这里我做了什么：
abstract class Component{
/**
* Used to access last chain Decorator
*
* @var Decorator
*/
protected $this;
protected $prop1;//These properies have to be accessed in any decorators
protected $prop2;
protected $prop3;
//this method is used to share properties with the childrens
public function getAttributesReferencesArray() {
$attributes=[];
foreach($this as $attr=>&$val)
$attributes[$attr]=&$val;
return $attributes;
}
}
class Foo extends Component{
public function __construct() {
$this->prop1="initialized";
//...
}
public function method1() {//this method can be "overrided" and called here
//...
}
public function method2() {//this method call the overrided or not method1
//...
$this->this->method1();
//...
}
}
abstract class Decorator extends Component{
/**
* Used to access parent component
*
* @var Component
*/
protected $parent;
public function __construct(Component $parent) {
$attributes=$parent->getAttributesReferencesArray();
foreach($attributes as $attr=>&$val)
$this->{$attr}=&$val;
$this->parent=$parent;
$this->this=$this;
}
public function __call($method, $args) {
if(!$this->parent instanceof Decorator &&
!method_exists($this->parent, $method))
throw new Exception("Undefined method $method attempt.");
return call_user_func_array(array($this->parent, $method), $args);
}
}
class Bar extends Decorator{
//this method call the component method (I guess Decorator classical way)
public function method1(){
//...
$this->parent->method1();
$this->prop2="set in Bar";
}
}
class Baz extends Decorator{
public function method2(){//this method call the overrided or not method1
//...
$this->this->method1();
//...
}
}
现在我们可以根据上下文“构造”“继承”了：
//...
$obj=new Foo();
if($context->useBar())
$obj=new Bar($obj);
if($context->somethingElse())
$obj=new Baz($obj);
并以行为抽象运行对象：
$obj->method1();
//...
它做我想要的，但是：
- 不再有封装
- $this->parent 很丑
- $this->这很难看
你怎么看？
- 如何以另一种方式访问装饰器（“儿童”）方法
- 我如何共享属性，例如它们是否在继承的上下文中受到保护
- 装饰器的使用不当吗？
- 有没有更优雅的模式可以解决问题
- parent 和这个属性是一种重新发明轮子，不是吗？
一个真实的例子：咖啡机
abstract class CoffeeFactory{// Component
/**
* Used to access last chain Decorator
*
* @var Decorator
*/
protected $this;
/**
* Used to access user choices
*
* @var CoffeeMachine
*/
protected $coffeeMachine;
protected $water;//the water quantity in cl
protected $coffeePowder;
protected $isSpoon=FALSE;
protected $cup=[];
//this method is used to share properties with the childrens
public function getAttributesReferencesArray() {
$attributes=[];
foreach($this as $attr=>&$val)
$attributes[$attr]=&$val;
return $attributes;
}
}
class SimpleCoffeeFactory extends CoffeeFactory{//Foo
public function __construct(CoffeeMachine $coffeeMachine) {
$this->coffeeMachine=$coffeeMachine;
$this->water=$coffeeMachine->isEspresso()?10:20;
$this->coffeePowder=$coffeeMachine->isDouble()?2:1;
$this->water-=$this->coffeePowder;
$this->this=$this;
}
private function addCoffeePowder(){
$this->cup["coffeePowder"]=$this->coffeePowder;
}
private function addSpoon(){
if($this->isSpoon)
$this->cup["spoon"]=1;
}
public function isWaterHot($boilingWater){
return $this->getWaterTemperature($boilingWater)>90;
}
private function addWater() {
$boilingWater=$this->getWaterForBoiling($this->water);
while(!$this->this->isWaterHot($boilingWater))
$this->boilWater($boilingWater);
$this->cup["water"]=$boilingWater;
}
public function prepare() {
$this->addCoffeePowder();
$this->addSpoon();
}
public function getCup() {
$this->this->prepare();
$this->addWater();
return $this->cup;
}
}
abstract class Decorator extends CoffeeFactory{
/**
* Used to access parent component
*
* @var Component
*/
protected $parent;
public function __construct(Component $parent) {
$attributes=$parent->getAttributesReferencesArray();
foreach($attributes as $attr=>&$val)
$this->{$attr}=&$val;
$this->parent=$parent;
$this->this=$this;
}
public function __call($method, $args) {
if(!$this->parent instanceof Decorator &&
!method_exists($this->parent, $method))
throw new Exception("Undefined method $method attempt.");
return call_user_func_array(array($this->parent, $method), $args);
}
}
class SugarCoffeeFactory extends Decorator{
protected $sugar;
public function __construct(Component $parent) {
parent::__construct($parent);
$this->sugar=$this->coffeeMachine->howMuchSugar();
$this->water-=$this->sugar;
$this->isSpoon=TRUE;
}
public function prepare() {
$this->cup['sugar']=$this->sugar;
$this->parent->prepare();
}
}
class MilkCoffeeFactory extends Decorator{
protected $milk;
public function __construct(Component $parent) {
parent::__construct($parent);
$this->milk=$this->coffeeMachine->howMuchMilk();
$this->water-=$this->milk;
}
public function prepare() {
$this->parent->prepare();
$this->cup['milk']=$this->milk;
}
public function isWaterHot($boilingWater){
//The milk is added cold, so the more milk we have, the hotter water have to be.
return $this->getWaterTemperature($boilingWater)>90+$this->milk;
}
}
//Now we can "construct" the "inheritance" according to the coffee machine:
//...
$coffeeFactory=new SimpleCoffeeFactory($coffeeMachine);
if($coffeeMachine->wantSugar())
$coffeeFactory=new SugarCoffeeFactory($coffeeFactory);
if($coffeeMachine->wantMilk())
$coffeeFactory=new MilkCoffeeFactory($coffeeFactory);
//and get our cup with abstraction of behaviour:
$cupOfCoffee=$coffeeFactory->getCup();
//...