Template Method em Ruby

# 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) 

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