From: Jamis Buck <jgb3@...>
Date: 2001-05-16T01:33:04+09:00
Subject: [ruby-talk:15176] Handling undefined methods gracefully

In Python, there is a pretty graceful way to specify a generic routine
to handle requests for attributes/methods that do not exist in an
object.  Is there a similar feature in Ruby?

For example, if I have a simple class:

class MySimpleClass
  def initialize
    @attrs = Hash.new
  end

  def []( name )
    @attrs[ name.downcase ]
  end

  def []=( name, value )
    @attrs[ name.downcase ] = value
  end
end


This (admittedly poor) example really just duplicates the functionality
of Hash table, but in a case-insensitive manner.

Now, the following code works great:

test = MySimpleClass.new
test[ 'Name' ] = "Jamis"
puts test[ 'name' ]

But what if I want to treat each new entry in the hash as an actual
attribute of the object (though internally continuing to use the hash
table to store and query the values), as follows:

test = MySimpleClass.new
test.name = "Jamis"
puts test.name

Using 'eval' I'm sure I could come up with something, but all the
scenarios I've thought of would be case-sensitive, and I would like to
find a way to do it such that 'name', 'Name', 'NAME', 'NaMe', etc. all
map to the same attribute, as is the case in the example above that uses
the [] method.

I hope I'm being clear here.  Is there a way to do this in Ruby, without
modifying the Ruby source code?  (Incidentally, I've already modified my
local copy of Ruby to support this, as an exercise...  but if there is
already support for this, that would naturally be preferable.)

Thanks for your help,

Jamis

-- 
Jamis Buck
minam@rpgplanet.com
http://www.rpgplanet.com/dnd3e/generators

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