行为型设计模式 - 责任链 Chain Of Responsibility
作者：菜皮日记
- 2023-09-08 北京
本文字数：1697 字
阅读完需：约 6 分钟
简介
使多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系。将这些对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它为止。
角色
Handler 接口
定义处理方法签名，设置 nextHandler 方法
Concrete Handler 具体类
实现各自 handler 逻辑
BaseHandler 封装一层 handler，可有可无
类图
如图，在 client 中，将 handler 一个个串起来，每个 handler 处理完后可决定是否向后传递。
类图
代码
interface Handler{ public function setNext(Handler $handler): Handler;
public function handle(string $request): string;}
abstract class AbstractHandler implements Handler{ private $nextHandler;
public function setNext(Handler $handler): Handler { $this->nextHandler = $handler; return $handler; }
public function handle(string $request): string { if ($this->nextHandler) { return $this->nextHandler->handle($request); }
return ""; }}
class MonkeyHandler extends AbstractHandler{ public function handle(string $request): string { if ($request === "Banana") { return "Monkey: I'll eat the " . $request . ".\n"; } else { return parent::handle($request); } }}
class SquirrelHandler extends AbstractHandler{ public function handle(string $request): string { if ($request === "Nut") { return "Squirrel: I'll eat the " . $request . ".\n"; } else { return parent::handle($request); } }}
class DogHandler extends AbstractHandler{ public function handle(string $request): string { if ($request === "MeatBall") { return "Dog: I'll eat the " . $request . ".\n"; } else { return parent::handle($request); } }}
function clientCode(Handler $handler){ foreach (["Nut", "Banana", "Cup of coffee"] as $food) { echo "Client: Who wants a " . $food . "?\n"; $result = $handler->handle($food); if ($result) { echo " " . $result; } else { echo " " . $food . " was left untouched.\n"; } }}
$monkey = new MonkeyHandler();$squirrel = new SquirrelHandler();$dog = new DogHandler();
$monkey->setNext($squirrel)->setNext($dog);
echo "Chain: Monkey > Squirrel > Dog\n\n";clientCode($monkey);
echo "\nSubchain: Squirrel > Dog\n\n";clientCode($squirrel);
复制代码
output:
Chain: Monkey > Squirrel > Dog
Client: Who wants a Nut? Squirrel: I'll eat the Nut.Client: Who wants a Banana? Monkey: I'll eat the Banana.Client: Who wants a Cup of coffee? Cup of coffee was left untouched.
Subchain: Squirrel > Dog
Client: Who wants a Nut? Squirrel: I'll eat the Nut.Client: Who wants a Banana? Banana was left untouched.Client: Who wants a Cup of coffee? Cup of coffee was left untouched.
复制代码
划线
评论
复制
发布于: 刚刚阅读数: 3
菜皮日记
关注
全干程序员 2018-08-08 加入
还未添加个人简介
评论