From: Kelly Felkins <kelly.felkins@...>
Date: 2005-08-09T23:30:53+09:00
Subject: help me understand this ruby idiom: class << self; alias_method :x :y end

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I'm trying to understand classes and objects. The Pick axe book points out=
=20
the "once" method in class Date and how it is defined using the object=20
singleton technique of "class << self". Actually Date uses this in several=
=20
places. Up until seeing Date I thought the reason for this idiom was to=20
add/replace methods in classes *when you don't have convenient access to th=
e=20
class definition* -- basically, use this when it's not your class you need=
=20
to enhance. But the fact that Date uses it several times indicates there is=
=20
another reason to use it.

Here are some examples from Date:
class << self; alias_method :leap?, :gregorian_leap? end
class << self; alias_method :new0, :new end

I just noticed that every use of class << self in Date contains an=20
alias_method.

Please enlighten me.

-Your humble pupil
Kelly

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