Comments on: Sustainable Development in Ruby, Part 1: Good Old-Fashioned Inheritance

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Sustainable Software Development | humandoing software — Thu, 25 Jun 2009 17:01:14 +0000

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By: Virtuous Code › Sustainable Development in Ruby, Part 2: Method Injection

Virtuous Code › Sustainable Development in Ruby, Part 2: Method Injection — Tue, 01 Apr 2008 02:00:12 +0000

[...] fields are marked * Name * Email * Website Comment add_openid_to_comment_form() ‹ Sustainable Development in Ruby, Part 1: Good Old-Fashioned Inheritance © 2008 ¶ Thanks, WordPress. ¶ veryplaintxt theme by Scott Allan Wallick. [...]

By: avdi

avdi — Sat, 29 Mar 2008 21:37:26 +0000

Pat: I understand your point, but this was the inheritance post Composition will come later.

By: Pat Maddox

Pat Maddox — Sat, 29 Mar 2008 21:05:57 +0000

I think this is a perfect example of where to prefer composition over inheritance. I would probably do:

class BufferedReader def initialize(connection) @connection = connection end

def receive buffer = "" begin message = @connection.receive buffer << message.data end until(message.data.include?("ENDENDEND")) Message.new(buffer) end end

This allows you to combine different readers to achieve the behavior you want. Not only that, but now the buffered reader is generally useful instead of being coupled to the Connection class.

By: avdi

avdi — Sat, 29 Mar 2008 19:37:26 +0000

Pat: I understand your point, but this was the inheritance post Composition will come later.

By: Pat Maddox

Pat Maddox — Sat, 29 Mar 2008 19:05:57 +0000

I think this is a perfect example of where to prefer composition over inheritance. I would probably do:

class BufferedReader
  def initialize(connection)
    @connection = connection
  end
  
  def receive
    buffer = ""
    begin
      message = @connection.receive
      buffer << message.data
    end until(message.data.include?("ENDENDEND"))
    Message.new(buffer)
  end
end

This allows you to combine different readers to achieve the behavior you want. Not only that, but now the buffered reader is generally useful instead of being coupled to the Connection class.