From: Thomas Sawyer <transfire@...>
Date: 2009-02-03T21:53:37+09:00
Subject: Re: Object#singleton_class in Ruby 1.9?

David A. Black wrote:

> etc. Jay's example with extending an object with two modules, so that
> the most recent one "wins" (whereas all modules "lose" if the method
> in question is defined in the singleton class) is very convincing,
> though again I wouldn't necessarily treat it as a reason never to
> define a method in the singleton class. I'd say it's more that you
> want to know what the ramifications of each technique are, and then
> choose the one you want. In that sense it's analogous (though not
> identical) to the non-singleton case, where a method defined in a
> class "wins", for the instances of the class, over definitions in
> included modules. That can be good, or not; it depends on what you're
> trying to do.
> 
> It all comes down to mastery of the order of method lookup, which then
> allows you to do pretty much any permutation.

Can you think of a good example of where it is NOT good? All I can think 
of is when we need to metaprogram around someone else not using modules.

I'm sure there are occasions to act directly on the singleton, but I've 
come to believe that should be the exception rather than the rule. And I 
think it would behoove Ruby to promote that as the common idiom. We've 
grown accustom to seeing "class << self". But I think it should be 
raising flags instead --"we are doing something very metay here".

T.
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