Re: To inherit or to include? That is the question.

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On Fri, Apr 04, 2003 at 11:39:55PM +0900, Robert Klemme wrote:
> Currently I can't see why you want to inherit a main function - if it's
> what I guess, then main is very application specific and does not lend
> itself easily for inheritance at all.

Perhaps not, but you probably wanted to inherit all the scaffolding around
it. For example, here is a simple but useful CGI application framework:

require 'fcgi'
class GUI
  def initialize(cgi)
    @cgi = cgi
    @done_header = false
  end

  def header(*args)
    return if @done_header
    puts @cgi.header(*args)
    @done_header = true
  end

  # def main: virtual

  def self.run
    FCGI.each_cgi do |cgi|
      begin
        app = self.new(cgi)
        app.main
      rescue Exception => detail
        app ? app.header : (puts cgi.header)
        print <<EOS
<html>
<head><title>Internal error in #{$0}</title></head>
<body>
<h1>Internal error in #{$0}</h1>
<b>#{CGI.escapeHTML(detail.message.to_s)}</b>
EOS
        puts "<pre>#{CGI.escapeHTML(detail.backtrace.join(\"\n\"))}</pre>" if detail.backtrace
        puts "</body></html>"
      end
    end
  end
end


You then create your application like this:

class MyGUI < GUI
  def main
    header
    name = @cgi['name'][0]
    if name
      puts "Hello #{name}"
    else
      puts "Who are you?"
    end
  end
end
MyGUI.run

That saves you a lot of work :-) The superclass 'GUI' could have lots of
other helper functions in it which you also might want to inherit.

Regards,

Brian.