行为型设计模式 - 模板方法 Template Method
作者：菜皮日记
- 2023-09-08 北京
本文字数：1774 字
阅读完需：约 6 分钟
简介
父类抽象类定义大的处理流程，部分细节做成抽象方法，留给子类去实现。
如 Java 的 JUnit 中， setUp tearDown 方法都是留给具体的测试用例来写，Servlet 中 service 处理了一个请求的大部分工作，留下 doGet 和 doPost 给业务自定义处理。
另外 callback 一般分两种方式：同步回调、异步回调，其中同步回调类似于模板方法模式，异步回调类似于观察者模式。
模板方法要基于继承，而回调更类似组合，
角色
抽象模板类
定义大的处理流程，留出部分方法给具体类实现
具体模板类
实现具体的处理逻辑
类图
如图，ConcreteClass 实现了一些具体逻辑
类图
代码
abstract class AbstractClass{ final public function templateMethod(): void { $this->baseOperation1(); $this->requiredOperations1(); $this->baseOperation2(); $this->hook1(); $this->requiredOperation2(); $this->baseOperation3(); $this->hook2(); }
protected function baseOperation1(): void { echo "AbstractClass says: I am doing the bulk of the work\n"; }
protected function baseOperation2(): void { echo "AbstractClass says: But I let subclasses override some operations\n"; }
protected function baseOperation3(): void { echo "AbstractClass says: But I am doing the bulk of the work anyway\n"; }
abstract protected function requiredOperations1(): void;
abstract protected function requiredOperation2(): void;
protected function hook1(): void { }
protected function hook2(): void { }}
class ConcreteClass1 extends AbstractClass{ protected function requiredOperations1(): void { echo "ConcreteClass1 says: Implemented Operation1\n"; }
protected function requiredOperation2(): void { echo "ConcreteClass1 says: Implemented Operation2\n"; }}
class ConcreteClass2 extends AbstractClass{ protected function requiredOperations1(): void { echo "ConcreteClass2 says: Implemented Operation1\n"; }
protected function requiredOperation2(): void { echo "ConcreteClass2 says: Implemented Operation2\n"; }
protected function hook1(): void { echo "ConcreteClass2 says: Overridden Hook1\n"; }}
function clientCode(AbstractClass $class){ $class->templateMethod();}
echo "Same client code can work with different subclasses:\n";clientCode(new ConcreteClass1());
echo "Same client code can work with different subclasses:\n";clientCode(new ConcreteClass2());
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output:
Same client code can work with different subclasses:AbstractClass says: I am doing the bulk of the workConcreteClass1 says: Implemented Operation1AbstractClass says: But I let subclasses override some operationsConcreteClass1 says: Implemented Operation2AbstractClass says: But I am doing the bulk of the work anywaySame client code can work with different subclasses:AbstractClass says: I am doing the bulk of the workConcreteClass2 says: Implemented Operation1AbstractClass says: But I let subclasses override some operationsConcreteClass2 says: Overridden Hook1ConcreteClass2 says: Implemented Operation2AbstractClass says: But I am doing the bulk of the work anyway
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