From: Robert Klemme <shortcutter@...>
Date: 2010-02-01T17:59:42+09:00
Subject: Re: manufacturing methods

2010/2/1 Josh Cheek <josh.cheek@gmail.com>:
> On Mon, Feb 1, 2010 at 1:05 AM, Matthew Pounsett <matt@conundrum.com> wrote:
>
>> Hi there.
>>
>> Apologies if this is covered somewhere... all the googling I've done on the
>> subject has wound up with info on class-factories and and using variables in
>> methods.  Not exactly what I'm looking for.
>>
>> The question I've got is related to manufacturing methods.  In my
>> particular case, I'm using a module that relies heavily on callback methods.
>>  I need to define a couple dozen callbacks which I'd like to all behave in
>> basically the same way.  In order to keep my code simple, I thought I'd try
>> manufacturing them all from the same basic code.. but haven't found a syntax
>> that works.
>>
>> Though this syntax clearly doesn't work, an example of the sort of thing
>> I'm looking for might look like this, assuming I want to create the methods
>> "on_foo", "on_bar", and "on_baz":
>>
>> %w( foo bar baz ).each do |callback|
>>   def on_#{callback}
>>      # callback work here
>>   end
>> end
>>
>> Is what I'm attempting to do even possible?
>>
>> Thanks,
>>  Matt
>>
>>
>>
>>
> If you are in a class, you should can do:
>
> class Test
>  %w( foo bar baz ).each do |callback|
>    define_method "on_#{callback}" do |param|
>      puts "This is method #{callback}"
>      puts "I have received the parameter: #{param}"
>      puts
>    end
>  end
> end
>
>
> test = Test.new
> (test.methods - Object.methods).each_with_index do |method,index|
>  test.send method , index
> end

In this case there is a much simpler solution which does not need
metaprogramming:

class X
  def on_event_impl(*a)
    printf "args=%p\n", a
  end

  alias foo on_event_impl
  alias bar on_event_impl
  alias baz on_event_impl
end

If you want to use a bit of metaprogramming in order to not repeat you can do:

class Y
  def on_event_impl(*a)
    printf "args=%p\n", a
  end

  %w{foo bar baz}.each {|m| alias_method m, :on_event_impl}
end

Yet another option is to use #method_missing

class Z
  def method_missing(s, *a, &b)
    if /\Aon_/ =~ s.to_s
      printf "args=%p\n", a
    else
      super
    end
  end
end

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/