From: Mauricio Fernandez <mfp@...>
Date: 2006-12-28T01:25:01+09:00
Subject: Re: Using an UnboundMethod instead of an alias to redefine a method

On Wed, Dec 27, 2006 at 11:30:05PM +0900, Daniel Berger wrote:
> I came across a technique for aliasing methods that I have never seen
> before [1] and was just too good to pass up.  But first, the setup.
[...] 
> So, now our custom Hash#[]= method is bound to an UnboundMethod that no
> one else has access to (see the first link below for a better
> explanation).  Pretty neat, eh? Is there any downside to this approach?
> If not, it seems this technique ought to be filed under 'best
> practices', and perhaps even abstracted somehow in the core itself.
> 
> Many thanks to Jay Fields [2], whose blog entry led me back to the
> original entry by Martin Traverso.

That technique is fairly old (I myself tried to popularize it a few years
ago). It's cleaner & generally safer than alias_method, but there are three
shortcomings:
* the environment captured by the closure is often too heavy (extra care
  needed to get rid of unwanted references is needed)
* a method defined with define_method+block cannot take a block under 1.8
  (it's possible in 1.9, though)
* method calls are much slower

[1] some other examples 
    http://thekode.net/ruby/techniques/CapturingMethods.html
-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby