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IWETHEY Home / IWETHEY Board / Theory and Practice of Programming Forum / Coming at it from the other way
Post #115,185
by johnu
8/24/03 3:13:15 PM
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New Coming at it from the other way
In Python, one can add functions to a class on the fly:

\n>>> class MyClass:\n... \tpass\n... \n>>> a = MyClass()\n>>> a.test()\nTraceback (most recent call last):\n  File "<interactive input>", line 1, in ?\nAttributeError: MyClass instance has no attribute 'test'\n>>> def myMethod(self, name):\n... \tprint "Hi from " + name\n... \t\n>>> myMethod(a, "stand alone")\nHi from stand alone\n>>> MyClass.test = myMethod \n>>> a.test("a class")\nHi from a class\n


Can this be done in a method oriented language like Ruby?

Regards,
John
Post #115,325
by JimWeirich
Picture of JimWeirich
8/25/03 4:44:26 PM
Reply
New Adding new methods in Ruby
Classes are always open in Ruby. New methods can be added at any time.

    # Create a new class\n    class MyClass\n    end\n\n    # Create an instance\n    a = MyClass.new\n\n    # Send a message for a non-existent method\n    a.f             # => NoMethodError: undefined method `f' for #<MyClass:0x1a1810>\n\n    # Open the class and add a new method\n    class MyClass\n      def f(name)\n        puts "Hi from #{name}"\n      end\n    end\n\n    # Now the instance will recognize the message\n    a.f("a class")  # => "hi from a class"
--
-- Jim Weirich jweirich@one.net [link|http://onestepback.org|http://onestepback.org]
---------------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct,
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)
     MOO/FOO and Python - (JimWeirich) - (11) - Aug. 22, 2003, 02:38:42 PM EDT
         Having done this before... - (admin) - (10) - Aug. 22, 2003, 02:41:18 PM EDT
             I'm not sure that's what I mean - (JimWeirich) - (9) - Aug. 22, 2003, 03:18:41 PM EDT
                 Like this: - (admin) - (4) - Aug. 22, 2003, 04:15:08 PM EDT
                     :) I haven't "gone meta" enough yet, I see... -NT - (FuManChu) - Aug. 22, 2003, 04:16:04 PM EDT
                     I came up with this ... - (JimWeirich) - (2) - Aug. 22, 2003, 05:52:21 PM EDT
                         I ran mine in 2.2.3, FYI - (admin) - (1) - Aug. 22, 2003, 06:02:50 PM EDT
                             My 2.2 is evidently broken - (JimWeirich) - Aug. 23, 2003, 08:25:55 AM EDT
                 AFAICT that hinges on method_missing... - (FuManChu) - Aug. 22, 2003, 04:15:17 PM EDT
                 You could also do this: - (admin) - Aug. 22, 2003, 04:21:57 PM EDT
                 Coming at it from the other way - (johnu) - (1) - Aug. 24, 2003, 03:13:15 PM EDT
                     Adding new methods in Ruby - (JimWeirich) - Aug. 25, 2003, 04:44:26 PM EDT

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