From: Steve Tu <lists@...>
Date: 2013-02-02T00:06:39+09:00
Subject: Re: Novice: self, @self.respond_to? and dynamically built methods

unknown wrote in post #1094752:
> Am 01.02.2013 12:36, schrieb Steve Tu:
>>
>>
>> if self.respond_to?(method)
>> What I want is to dynamically build a method name, then see if the
>> object (in this case 'self' or the current module) supports that method
>> and if so to then execute that method with any optional arguments.
>
> To me, this does not sound like a use case for metaprogramming.
> Why don't you use a method that takes the section as an argument?
>
>
> But to your question: I assume you are talking about 'global' methods?
> If so, I cannot reproduce your problem:
>
>
> 1.9.3p374 :001 > def test_method; puts 'test'; end
>   => nil
> 1.9.3p374 :002 > self.methods.include?(:test_method)
>   => true
> 1.9.3p374 :003 > test_method
> test
>   => nil
> 1.9.3p374 :004 > self.send(:test_method)
> test
>   => nil
> 1.9.3p374 :005 > self.respond_to?(:test_method)
>   => true

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'

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

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