go责任链行为型设计模式Chain Of Responsibility
作者：菜皮日记
这篇文章主要为大家介绍了go行为型设计模式之责任链Chain Of Responsibility使用示例详解,有需要的朋友可以借鉴参考下,希望能够有所帮助,祝大家多多进步,早日升职加薪
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。
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);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.
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