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    <p>No, it has been replaced by a clever use of method overriding in modules and the <code>super</code> keyword.</p> <p>Basically, you define the original function in an included module, and override it in another included module. When you call <code>super</code> in the overriding function, it calls the original function. But there is one catch. You have to include the extending modules <strong>after</strong> including the base module, and in the order you want the chaining to occur.</p> <pre><code>class Something module Base def my_method # (A) original functionality end end module PreExtension def my_method # (B) before the original super # calls whatever was my_method before this definition was made end end module PostExtension def my_method super # calls whatever was my_method before this definition was made # (C) after the original end end include Base # this is needed to place the base methods in the inheritance stack include PreExtension # this will override the original my_method include PostExtension # this will override my_method defined in PreExtension end s = Something.new s.my_method #=&gt; this is a twice extended method call that will execute code in this order: #=&gt; (B) before the original #=&gt; (A) the original #=&gt; (C) after the original </code></pre> <p>Ryan Bates of <a href="http://railscasts.com" rel="nofollow noreferrer">Railscasts</a> talks about <a href="http://railscasts.com/episodes/232-routing-walkthrough-part-2" rel="nofollow noreferrer">how this is used in the Rails Routing code</a>. I'd recommend watching it, and his other screencasts. They have the power to transform a knitting grandmother into a Rails guru.</p> <p><em>PS: Credit goes to <a href="https://stackoverflow.com/users/4937/peeja">Peeja</a> for correcting a fundamental error in my original answer. Thanks.</em></p>
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    1. COSweet! Thanks. I have watched most of the Railscasts I just hadn't seen that one yet.
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    2. COVery Clever Hack, much nicer than using the alias built-in of the langage too...
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    3. COI don't believe that's correct. By my understanding and this experiment, the modules' methods are never called: https://gist.github.com/664352
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