geckofu/template_method_pattern.rb

## template_method_pattern.rb
# Template Method Pattern relies on inheritance
class Report
  def initialize
    @title = 'Monthly Report'
    @text = ['Things are going', 'really, really well.']
  end

  def output_report
    output_start
    output_head
    @text.each do |line|
      output_line(line)
    end
    output_end
  end

  def output_start
  end

  def output_head
    raise 'Abstract method called: output_head'
  end

  def output_end
  end
end


class HTMLReport < Report
  def output_start
    puts('<html>')
  end

  def output_head
    puts('<head>')
    puts("<title>#{@title}</title>")
    puts('</head>')
  end

  def output_line(line)
    puts("<p>#{line}</p>")
  end

  def output_end
    puts('</html>')
  end
end


def PlainTextReport < Report
  def output_head
    puts("**** #{@title} ****")
  end

  def output_line(line)
    puts(line)
  end
end


# One characteristic that the HTMLReport and PlainTextReport share is that they look fragmentary.
# Cause they do not override the key template method, output_report.
# In the Template Method pattern, the abstract base class controls the higher-level processing
# through the template method; the sub-classes simply fill in the details.
	# Template Method Pattern relies on inheritance
	class Report
	def initialize
	@title = 'Monthly Report'
	@text = ['Things are going', 'really, really well.']
	end

	def output_report
	output_start
	output_head
	@text.each do \|line\|
	output_line(line)
	end
	output_end
	end

	def output_start
	end

	def output_head
	raise 'Abstract method called: output_head'
	end

	def output_end
	end
	end


	class HTMLReport < Report
	def output_start
	puts('<html>')
	end

	def output_head
	puts('<head>')
	puts("<title>#{@title}</title>")
	puts('</head>')
	end

	def output_line(line)
	puts("<p>#{line}</p>")
	end

	def output_end
	puts('</html>')
	end
	end


	def PlainTextReport < Report
	def output_head
	puts("** #{@title} **")
	end

	def output_line(line)
	puts(line)
	end
	end


	# One characteristic that the HTMLReport and PlainTextReport share is that they look fragmentary.
	# Cause they do not override the key template method, output_report.
	# In the Template Method pattern, the abstract base class controls the higher-level processing
	# through the template method; the sub-classes simply fill in the details.