From: Erik Veenstra <pan@...>
Date: 2006-02-08T07:33:21+09:00
Subject: Re: Meta-Meta-Programming


I forgot to show you the implementation of this "typed".

Well, here it is...

gegroet,
Erik V. - http://www.erikveen.dds.nl/

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         # IMPLEMENTATION

 class Module
   def typed(method_name, *types)
     wrap_method(method_name) do |org_method, args, block|
       args.each_with_index do |args, n|
         [types[n]].flatten.each do |typ|
           if typ.kind_of?(Module)
             unless arg.kind_of?(typ)
               raise ArgumentError, "Wrong argument type (#{arg.class} instead of #{typ}, argument #{n+1})."
             end
           elsif typ.kind_of?(Symbol)
             unless arg.respond_to?(typ)
               raise ArgumentError, "#{arg} doesn't respond to :#{typ} (argument #{n+1})."
             end
           else
             raise ArgumentError, "Wrong type in types (#{typ}, argument #{n+1})"
           end
         end
       end

       org_method.call(*args, &block)
     end
   end
 end

----------------------------------------------------------------

         # TEST SCRIPT

 class Foo
   def bar(x, y, z)
     # x should be Numeric
     # y should be a String
     # z should respond to :gsub and :to_s
     :good
   end

   typed :bar, Numeric, String, [:gsub, :to_s]
 end

 def test(*args)
   begin
     puts "#{args.inspect} : OK : #{Foo.new.bar(*args).inspect}"
   rescue Exception => e
     puts "#{args.inspect} : NOK : #{e.message}"
   end
 end

 puts
 puts File.open(__FILE__){|f| f.readlines}.select{|x| x =~ /^\s*typed\b/}.join("\n")
 puts

 test(7)
 test(7, 8, 9)
 test(7, 8, "9")
 test(7, "8", 9)
 test(7, "8", "9")

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