Template Method en Ruby

Template Method es un patrón de diseño de comportamiento que te permite definir el esqueleto de un algoritmo en una clase base y permite a las subclases sobrescribir los pasos sin cambiar la estructura general del algoritmo.

Aprende más sobre el patrón Template Method

Complejidad:

Popularidad:

Ejemplos de uso: El patrón Template Method es muy común en los frameworks Ruby. Los desarrolladores lo utilizan a menudo para proporcionar a los usuarios de frameworks medios sencillos para extender la funcionalidad estándar utilizando la herencia.

Identificación: El patrón Template Method se puede reconocer por los métodos de comportamiento que ya tienen un comportamiento “por defecto” definido por la clase base.

Ejemplo conceptual

Este ejemplo ilustra la estructura del patrón de diseño Template Method. Se centra en responder las siguientes preguntas:

¿De qué clases se compone?
¿Qué papeles juegan esas clases?
¿De qué forma se relacionan los elementos del patrón?

main.rb: Ejemplo conceptual

# 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: Resultado de la ejecución

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

Template Method en Ruby

Ejemplo conceptual

main.rb: Ejemplo conceptual

output.txt: Resultado de la ejecución

Template Method en otros lenguajes