（六）面向对象的设计原则之二

一．简介：

命令模式：命令模式分为“命令的请求者”和“命令的实现者”。使得命令的请求和实现完成了解耦。
二．示例：

<?php
/*
* 模拟服务员与厨师
*/
class MealCommand implements Command{
private $cook;
public function __construct(cook $cook){
$this->cook = $cook;
}
public function execute(){
$this->cook->meal();
}
}

class DrinkCommand implements Command{
private $cook;
public function __construct(cook $cook){
$this->cook = $cook;
}

public function execute(){
$this->cook->drink();
}
}

/*
* 模拟类
*/
class cookControl{
private $mealCommand;
private $drinkCommand;

public function addCommand(Command $mealCommand,Command $drinkCommand){
$this->mealCommand = $mealCommand;
$this->drinkCommand = $drinkCommand;
}

public function callMeal(){
$this->mealCommand->execute();
}

public function callDrink(){
$this->drinkCommand->execute();
}
}

$control = new cookControl();
$cook = new cook;
$mealCommand = new MealCommand($cook);
$drinkCommand = new DrinkCommand($cook);
$control->addCommand($mealCommand,$drinkCommand);
$control->callMeal();
$control->callDrink();
三．使用原则：

1.根据业务流程，提炼业务流程。一步步抽象直至‘恰当’。

2.职责分类需要注意。