From: bbense+comp.lang.ruby.Sep.27.02@...
Date: 2002-09-28T03:03:32+09:00
Subject: Re: Ruby program design question ( Pattern or AntiPattern ?)

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In article <51172973522.20020927095543@integ.ru>,
Bulat Ziganshin <bulatz@integ.ru> wrote:
>Hello bbense+comp,
>
>Thursday, September 26, 2002, 11:36:24 PM, you wrote:
>
>bclrS20tse> - - I find myself repeating this kind of pattern over and over
>bclrS20tse>   again. I'm wondering if it's a good sign or a bad one. Here's
>bclrS20tse>   the pattern. 
>
>bclrS20tse>   Write a simple generic ruby class to interface to something. 
>
>delegation pattern? please provide code example
>

- - Here's a trivial example. I've been using ifile to help sort
  spam in my ruby mailhandler. Here's the ifile class

#
# $Id: ifile.rb,v 1.1 2002/09/25 20:02:13 bbense Exp $
#
# Ifile, a class for interacting with ifile program.
# Get ifile at http://www.ai.mit.edu/~jrennie/ifile/
#
# Booker C. Bense <bbense@slac.stanford.edu> 
#

require 'open3'

module Ifile

# This is the wrong name, but I can't think of anything better.
class Process
  # Tell me where ifile lives.
  def initialize(path="/var/local/bin/ifile",args="--verbosity=0") 
    if FileTest.executable?(path) then 
      @ifile = path
      @args = args
    else
      raise ArgumentError 
    end 
  end

  # Given a message, query folders

  def query(msg)
    results = Array.new
    output = self.run_ifile(msg,"--query ")
    i = 0 
    output.each do |line|
      # Format of output is folder score
      folder , score = line.split
      if ( folder && score ) then 
	tmp = Hash.new
	tmp['folder'] = folder
	tmp['score'] = score.to_f
	tmp['position'] = i 
	results << tmp 
	i = i + 1 
      end
    end 
    return results
  end 

  # Add a message to a folder
  def add(msg,folder)
    output = self.run_ifile(msg,"--insert=#{folder}") 
  end
  # Delete a message from a folder
  def delete(msg,folder) 
    output = self.run_ifile(msg,"--delete=#{folder}") 
  end 

  # Refile
  def refile(msg,oldfolder,newfolder) 
    self.delete(msg,oldfolder) 
    self.add(msg,newfolder)
  end 
# internal methods
  
  
  def run_ifile(msg,args) 
    stdin, stdout, stderr = Open3.popen3("#{@ifile} #{@args} #{args}")
    #write msg to ifile
    msg.each { |line| stdin.puts line } 
    stdin.close
    #Read output 
    output = stdout.readlines
    stdout.close
    stderr.close
    return output
  end 


end


end # module Ifile
 

- - I used this module in several programs, sometimes
I can use it without a "controller" , however I tend
to end up writing stuff like this. 


# For dealing with ifile
class IfileProcess

  def initialize(filterdir,default_folder)
    @filterdir = filterdir
    @default_folder = default_folder

    @ifile = Ifile::Process.new
    @same = Hash.new
    @same["unix-admin"] = "oldmail"
    @same["admin-log"]  = "oldmail"
    @same[default_folder] = "oldmail"
  end

# Return a full fledge path 
  def query(msg)
    results = @ifile.query(msg) 
    best = results[0]["folder"]
    if ( @same[best] ) then
      return @default_folder
    end 
    dest = "#{@filterdir}/#{best}"
    dest.sub!(/\s/,"")
    return dest
  end 

  def add(msg,destination)
    if ( @same[destination] ) then
      folder = @same[destination]
    else
      folder = destination.sub(@filterdir,"")
      folder.sub!(/[\/]/,"")
      # Deal with incoming/oldmail problem 
      if ( @same[folder]  ) 
	folder = @same[folder] 
      end
    end
    print "Adding message to :#{folder}:\n"
    @ifile.add(msg,folder)
  end

end #IfileProcess


- - As you can see IfileProcess has a bunch of icky
knowledge about other classes and default paths
that I have kept out of the simple class. Now that
I think about it I could probably just as easily
implement these as subclasses of the original 
class. It never occurs to me to do that however.

- - Booker C. Bense 

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