From: sto.mar@...
Date: 2013-02-01T22:38:11+09:00
Subject: Re: Novice: self, @self.respond_to? and dynamically built methods

Am 01.02.2013 12:36, schrieb Steve Tu:
> I have been plodding through a Ruby tutorial and came across the
> 'require'
> and 'load' methods(?). Prior to that, all of the tutorial examples I
> played with had been bolted into one file. I had added in a 'zenity'
> based menu option to drive the selection of the tutorial subjects.
> Now I have split each of the tutorial subjects into separate files that
> get 'loaded' or 'required'. The 'main' section is then just a  call to
> the zenity menu driver, and calls to the respective methods.
>
> All works fine...apart from...
>
> I had an old tutorial module that looked at the passing of arguments
> into Ruby from the command line. This example did little more than split
> the arguments into the argument type and value and then displayed them.
> I thought it would be nice then to revisit this and make the argument
> type the name of a tutorial 'method' and the argument value any value
> required by that tutorial method.
>
> This seemed relatively straight forward, so I could now call my Ruby
> module as:
> ./ptutorial.rb -s"HASHES" -o"1"
>
>  From my driver menu, I could then select the argument tutorial - and it
> would split the two arguments into a variable containing a method name
> (by downcasing and appending _test to the -s argument) and option
> variable.
>
> Now, to stop a call to a non existent method, I wanted to see if the
> built method variable existed as a method.
>
> What I thought I could then do, was to see if 'self' responded to the
> method by using:
> if self.respond_to?(method)
>
> but it seems that 'self' does not respond to that method - although if I
> call self.send(method, option) it appears to work fine (even though if I
> look at the methods that self/@self supports via the methods method,
> none of my 'local' tutorial methods appear).
>
> I thought that it may be down to use of 'self' as opposed to '@self' but
> both fail on the respond_to?, and seem to process the method ok on the
> send.
>
> 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






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