meta_methods.rb

class Computer
  def initialize(computer_id,data_source)
    @id = computer_id
    @data_source = data_source
  end 
  
  def mouse
    info = @data_source.get_mouse_info(@id)
    price = @data_source.get_mouse_price(@id)
    result = "Mouse:#{info}($#{price})"
    return "*#{result}" if price>=100
    result
   end
  
  def cpu
    info = @data_source.get_cpu_info(@id)
    price = @data_source.get_cpu_price(@id)
    result = "Cpu:#{info}($#{price})"
    return "*#{result}" if price>=100
    result
   end
  
  def keyboard
    info = @data_source.get_keyboard_info(@id)
    price=@data_source.get_keyboard_price(@id)
    result="Keyboard:#{info}($#{price})"
    return "*#{result}" if price>=100
    result
  end
end

# Refactored by adding dynamic dispatches 

class Computer
  def initialize(computer_id, data_source)
    @id = computer_id
    @data_source = data_source
  end 
  
  # call to each method is delegated to component
  def mouse
    component :mouse
   end
  
  def cpu
    component :cpu
   end
  
  def keyboard
    component :keyword
  end
  
  def component(name)
    info = @data_source.send "get_#{name}_info", (@id)
    price= @data_source.send "get_#{name}_price", (@id)
    result= "#{name.capitalize}: #{info}($#{price})"
    return "*#{result}" if price>=100
    result
  end
end

# Generating method dynamically 
class Computer
  def initialize(computer_id, data_source)
    @id = computer_id
    @data_source = data_source
  end 
  
  def self.define_component(name)
    define_method(name) do
      info = @data_source.send("get_#{name}_info", @id)
      price = @data_source.send("get_#{name}_price", @id)
      result = "#(name.capitalize}: #{info} ($#{price})"
      return "#{result}" if price >= 100
      result
    end
  end
  
  define_component :mouse
  define_component :cpu
  define_component :keyboard
end

# refactor using method_missing 
class Computer
  def initialize(computer_id, data_source)
    @id = computer_id
    @data_source = data_source
  end 
  
  def method_missing(name)
    super if !@data_source.respond_to?("get_#{name}_info")
    info = @data_source.send("get_#{name}_info", @id)
    price = @data_source.send("get_#{name}_price", @id)
    result = "#(name.capitalize}: #{info} ($#{price})"
    return "#{result}" if price >= 100
    result
  end
end