From: sto.mar@...
Date: 2013-02-02T00:58:59+09:00
Subject: Re: Novice: self, @self.respond_to? and dynamically built methods

Am 01.02.2013 16:06, schrieb Steve Tu:

> The code I have is now split into separate files that are 'load' or
> 'require'd. The argument test file contains:
>   #-----------------------------------------------------------------------
>   #   F O R M A L   A R G U M E N T S
>   #-----------------------------------------------------------------------
>    def arguments_test
>      require 'getoptlong'

I like optparse.

>
>      # The parameters can be in any order
>      STDOUT.puts "Arguments "+ARGV.length.to_s

puts uses stdout by default, so you can just use `puts'.

>      unless ARGV.length >= 1
>          `zenity --info --title="Usage ... " --text="Usage:
> ./ptutorial.rb -s\"Subject\" -o\"Options\""`
>          exit
>      end
>
>      subject = option =  ''
>      # specify the options we accept and initialize
>      # the option parser
>      opts = GetoptLong.new(
>                  [ "--subject", "-s", GetoptLong::REQUIRED_ARGUMENT ],
>                  [ "--option", "-o", GetoptLong::OPTIONAL_ARGUMENT ],
>              )
>      # process the parsed options
>      opts.each do |opt, arg|
>          case opt
>              when '--subject'
>                  subject = arg
>              when '--option'
>                  option = arg
>          end
>      end
>
>      STDOUT.puts "(#{self}) - (#{self.to_s}) Supports (#{self.methods})"

#{self} sends to_s implicitly, so #{self} and #{self.to_s} are the same

>      STDOUT.puts "No Class Supports (#{methods})"
>
>
>      method  = "#{subject.to_s.chomp.downcase}_test"
>      if self.respond_to?(method)
>          self.send(method)
>      else
>          if self.respond_to?(method,TRUE)
>              self.send(method,option)
>          else
>              `zenity --info --title="Arguments ... " --text="Args:
> (#{@self}).... Does Not Support #{method}"`
>          end
>      end
>
>      `zenity --info --title="Arguments ... " --text="Args: Subject
> (#{subject}) Option (#{option})"`
>
>    end
>
>
> What I now end up with is the 'private' respond_to? test working - which
> is one point I don't understand (ie what determines a method's
> visibility - I thought it had to be explicitly defined or was assumed as
> public?).

Seems 'global' methods behave differently, they are private methods
of `Object', see 
http://stackoverflow.com/questions/8799704/are-ruby-imported-methods-always-private

> That then lead onto the question re how to determine the
> footprint of the method being called, as the code above works if the
> method passed accepts a single parameter. If the method accepts o
> parameters then the code fails anyway - and hence the question re
> whether it is simply then better to just attempt the method call and
> trap the errors thrown, rather than trying to see if the method is
> supported in the first place.
> Am I making any sense at all?

You could use an optional argument hash.


Still, this approach seems a bit strange to me.
Ever thought about defining classes?


-- 
<https://github.com/stomar/>