Ruby Design Pattern

template pattern

write abstract method in base class.

In ruby raise in abstract method to make sure it’s implemented in subclass.

Hook is the so called empty method in base class.

class Base
  def abstract_method
    raise "this method need to be implemented"
  end
  def hook_method
   #just do nothin here but can be implemented to so something in subclass
  end
end




class Sub < Base
  def abstract_method
    # implemented the method
  end


  def hook_method
    # implement the method
  end
end

Example of this pattern in ruby: GenerickServer in webrick

Strategy pattern

The GoF call this “pull the algorithm out into a separate object” technique the Strategy pattern

# pull the algorithm of renderer outside of the class
class Reporter
  def initialize(content, renderer)
     @content = content
     @renderer = renderer  
  end
  def render
     @renderer.render(@content)
  end
end


class MarkdownRenderer
  def self.render(content)
    # markdown render
  end
end


class HTMLRenderer 
  def self.render(content)
    # html render
  end
end


content = "##title##"
htmlReport = Reporter.new(content, HTMLRenderer)
markdownReport = Reporter.new(content, MarkdownRenderer)

Thanks for Ruby’s duck typing, we don’t need to have a base abstract class for the Renderer. We only need to make sure a class method render is defined

Even we can use a callable proc to remove the class declaration.

Example of this pattern in ruby: the Auth middle-ware Warden

Observer pattern

Take ActiveRecord hooks as an Example.

n a nice example of the Convention Over Configuration pattern (see Chapter 18), ActiveRecord does not require you to register your observer: It just figures out that EmployeeObserver is there to observe Employees, based on the class name

ruby design pattern

template pattern

write abstract method in base class.

In ruby raise in abstract method to make sure it’s implemented in subclass.

Hook is the so called empty method in base class.

class Base
  def abstract_method
    raise "this method need to be implemented"
  end
  def hook_method
   #just do nothin here but can be implemented to so something in subclass
  end
end




class Sub < Base
  def abstract_method
    # implemented the method
  end


  def hook_method
    # implement the method
  end
end

Example of this pattern in ruby: GenerickServer in webrick

Strategy pattern

The GoF call this “pull the algorithm out into a separate object” technique the Strategy pattern

# pull the algorithm of renderer outside of the class
class Reporter
  def initialize(content, renderer)
     @content = content
     @renderer = renderer  
  end
  def render
     @renderer.render(@content)
  end
end


class MarkdownRenderer
  def self.render(content)
    # markdown render
  end
end


class HTMLRenderer 
  def self.render(content)
    # html render
  end
end


content = "##title##"
htmlReport = Reporter.new(content, HTMLRenderer)
markdownReport = Reporter.new(content, MarkdownRenderer)

Thanks for Ruby’s duck typing, we don’t need to have a base abstract class for the Renderer. We only need to make sure a class method render is defined

Even we can use a callable proc to remove the class declaration.

Example of this pattern in ruby: the Auth middle-ware Warden

Observer pattern

Take ActiveRecord hooks as an Example.

n a nice example of the Convention Over Configuration pattern (see Chapter 18), ActiveRecord does not require you to register your observer: It just figures out that EmployeeObserver is there to observe Employees, based on the class name