From: James Edward Gray II <james@...>
Date: 2007-05-31T00:28:33+09:00
Subject: Re: #respond_to? not working for dynamically generated metho

On May 30, 2007, at 9:57 AM, Maurice Gladwell wrote:

> It would be interesting to see an implementation of James Edward  
> Gray's
> suggestion above. ("You use an Extract Method refactoring to pull out
> the matching logic into a separate private method and use that in
> both implementations.")

#!/usr/bin/env ruby -wKU

class Test
   def initialize(*fields)
     @fields = fields.map { |f| f.to_s }
   end

   def find(*args)
     "Performing query with args:\n#{args.inspect}"
   end

   def method_missing(meth, *args, &block)
     if find_args = dynamic_finder?(meth)
       find( find_args.first,
             :conditions => find_args[1..-1].zip(args).
                                             map { |n, v| "#{n} = '# 
{v}'"}.
                                             join(" AND ") )
     else
       super
     end
   end

   def respond_to?(*args)
     super || dynamic_finder?(args.first)
   end

   private

   def dynamic_finder?(method_call)
     if method_call.to_s =~ /\Afind(_all)?_by_(\w+)\Z/
       args =  [$1 ? :all : :first]
       args += $2.split("_and_")
       args if args[1..-1].all? { |f| @fields.include? f }
     end
   end
end

if __FILE__ == $PROGRAM_NAME
   model = Test.new(:name, :age, :height, :weight)

   p !!model.respond_to?(:find_by_name_and_height)
   p !!model.respond_to?(:find_all_by_age)
   p !!model.respond_to?(:find_all_by_race)

   puts

   puts model.find_by_name_and_height("James", "61 in.")
   puts model.find_all_by_name_and_height
end

James Edward Gray II