From: Charles Comstock <cc1@...>
Date: 2004-07-08T08:17:34+09:00
Subject: Re: Class#=== has interesting results

> Ack.
> 
> And a question to the OP: why do you want to apply the case statement to 
> classes instead of to their instances? What should this case statement 
> do (depending on which class is given)? Maybe we can find an alternative 
> to what you think you need.
> 
> Regards,
> Pit
> 
> 
   def parse(str)
     input = str.chomp.split
     comm = CommandFactory[input[0]]

     case comm
     when StartCommand
       comm.new(input[1],input[2..-1])
       @mobile = input[1]
     when HelpCommand
     else
       comm.new(@mobile,input[1..-1])
     end
   end

CommandFactory returns the name of the class so that can instantiate it 
later with different arguments.  Normally all commands reference who 
they are from but the start command and help are different since the 
start command defines who it is from, and the help command needs to be 
accessable before and after the start command has actually instantiated 
a character.  I could pass these as parameters later on through a 
different function, but this seemed a logical way to do it.  I think 
this should work:

   def parse(str)
     input = str.chomp.split
     comm = CommandFactory[input[0]]

     case comm.id
     when StartCommand.id
       comm.new(input[1],input[2..-1])
       @mobile = input[1]
     when HelpCommand.id
     else
       comm.new(@mobile,input[1..-1])
     end
   end

Since we are matching id's now which is valid.  The command factory part 
is actually pretty slick too, there is a Command superclass and whenever 
anything derives from it, self.inherited gets called on Command, which 
then grabs the singleton instance of CommandFactory and adds the 
inherited class name to a hash in CommandFactory.  So CommandFactory has 
a hash which amoung other things includes {"start" => StartCommand, 
"help" => HelpCommand}, so when I parse the commandline I just grab the 
needed command right out of the CommandFactory and then instantiate it 
with the rest of the commandline parameters.

It's just a stupid mud project I am doing to test out pattern based 
software design.  When it's finished I'll release it to the community as 
example code.

I think id should fix my problem, it just suprised me when it didn't 
match the name like I thought it would.

Charles Comstock