From: "trans.  (T. Onoma)" <transami@...>
Date: 2004-11-23T23:55:24+09:00
Subject: Generalizing and Organizing Code

I am finding it difficult to properly generalize and organize my code. Perhaps 
others can offer some advice.  Here is a snip two related parts. I have about 
five others like these:

    # section
    def parse_section_set_tab? ; false ; end
    def parse_section_set_tab ; tab ; end
    def parse_section?( line, tab )
      true
    end
    def parse_section_skip? ; false ; end
    def parse_section( block )
      text = block.collect{ |line| line.text }.join("\n")
      md = /([=]+)[ ]*(.*?)[ ]*[=]+/.match( text )
      raise "Unexpeted match error" unless md
      level = md[1].length
      title = md[2]
      dobj = ArtML::DOM::Section.new( level, title )
      
      until level > @document_stack.last.level do
        @document_stack.pop
      end
      @document_stack.last << dobj    # add this section to its parent
      @document_stack << dobj         # and pop it on
    end
    
    
    # paragraph
    def parse_paragraph_set_tab? ; true ; end
    def parse_paragraph_set_tab( line, tab ) ; line.indent ; end
    def parse_paragraph?( line, tab )
      line.kind != :paragraph or line.indent > tab
    end
    def parse_paragraph_skip? ; false ; end
    def parse_paragraph( block )
      text = block.collect{ |line| line.text }.join("\n")
      content = text #parse_inline( text )
      @document_stack.last << ArtML::DOM::Paragraph.new( content )
    end

In the generalized code these are called using #send. Eg.

  if send("parse_#{state}?", line, tab)
    send("parse_#{state}", block)
  end

As you can see, I am using a name prefix "trick" to encapsulate these.  I 
would like to encapsulate them better, but I have a couple of difficulties. 
My first problem is the use of @document_stack which they all work on. The 
second problem is that I'm not sure what the encapsulation would be --they 
consist of both data and code (but not state), yet there is only ever one of 
each, so they aren't classes. And yet they don't seem like objects either b/c 
the code differs between each of them. Perhaps use a module? That only seems 
to adjust the name trick (Paragraph::parse instead of paragraph_parse). Plus, 
I then have to do 'class << self', which seems ugly to me. Nor does it seem 
like that's how a "module" is meant to be used.

What is the proper way to handle this in a class-based OOPL?

Thanks,
T.