Ruby 模板方法模式讲解和代码示例
模版方法是一种行为设计模式， 它在基类中定义了一个算法的框架， 允许子类在不修改结构的情况下重写算法的特定步骤。
复杂度：
流行度：
使用示例： 模版方法模式在 Ruby 框架中很常见。 开发者通常使用它来向框架用户提供通过继承实现的、 对标准功能进行扩展的简单方式。
识别方法： 模版方法可以通过行为方法来识别， 该方法已有一个在基类中定义的 “默认” 行为。
概念示例
本例说明了模板方法设计模式的结构并重点回答了下面的问题：
- 它由哪些类组成？
- 这些类扮演了哪些角色？
- 模式中的各个元素会以何种方式相互关联？
main.rb: 概念示例
# The Abstract Class defines a template method that contains a skeleton of some # algorithm, composed of calls to (usually) abstract primitive operations. # # Concrete subclasses should implement these operations, but leave the template # method itself intact. class AbstractClass # The template method defines the skeleton of an algorithm. def template_method base_operation1 required_operations1 base_operation2 hook1 required_operations2 base_operation3 hook2 end # These operations already have implementations. def base_operation1 puts 'AbstractClass says: I am doing the bulk of the work' end def base_operation2 puts 'AbstractClass says: But I let subclasses override some operations' end def base_operation3 puts 'AbstractClass says: But I am doing the bulk of the work anyway' end # These operations have to be implemented in subclasses. def required_operations1 raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'" end # @abstract def required_operations2 raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'" end # These are "hooks." Subclasses may override them, but it's not mandatory # since the hooks already have default (but empty) implementation. Hooks # provide additional extension points in some crucial places of the algorithm. def hook1; end def hook2; end end # Concrete classes have to implement all abstract operations of the base class. # They can also override some operations with a default implementation. class ConcreteClass1 < AbstractClass def required_operations1 puts 'ConcreteClass1 says: Implemented Operation1' end def required_operations2 puts 'ConcreteClass1 says: Implemented Operation2' end end # Usually, concrete classes override only a fraction of base class' operations. class ConcreteClass2 < AbstractClass def required_operations1 puts 'ConcreteClass2 says: Implemented Operation1' end def required_operations2 puts 'ConcreteClass2 says: Implemented Operation2' end def hook1 puts 'ConcreteClass2 says: Overridden Hook1' end end # The client code calls the template method to execute the algorithm. Client # code does not have to know the concrete class of an object it works with, as # long as it works with objects through the interface of their base class. def client_code(abstract_class) # ... abstract_class.template_method # ... end puts 'Same client code can work with different subclasses:' client_code(ConcreteClass1.new) puts "\n" puts 'Same client code can work with different subclasses:' client_code(ConcreteClass2.new) output.txt: 执行结果
Same client code can work with different subclasses: AbstractClass says: I am doing the bulk of the work ConcreteClass1 says: Implemented Operation1 AbstractClass says: But I let subclasses override some operations ConcreteClass1 says: Implemented Operation2 AbstractClass says: But I am doing the bulk of the work anyway Same client code can work with different subclasses: AbstractClass says: I am doing the bulk of the work ConcreteClass2 says: Implemented Operation1 AbstractClass says: But I let subclasses override some operations ConcreteClass2 says: Overridden Hook1 ConcreteClass2 says: Implemented Operation2 AbstractClass says: But I am doing the bulk of the work anyway 
