From: Brian Mitchell <binary42@...>
Date: 2007-12-13T23:52:17+09:00
Subject: Re: Is there any way to redefine the `new' method?

On Dec 13, 2007 9:35 AM, pluskid <pluskid@gmail.com> wrote:
> Hi! I'm writing a toy interpreter for scheme in Ruby. I created a
> class to represent scheme Symbol.
> And as the scheme Symbol, I want only one instance for symbols with
> the same name. I try to
> do it like this:
>
> class Symbol
>   alias orig_new new
>   def new(name)
>     @@symbols[name] ||= orig_new(name)
>     @@symbols[name]
>   end
> end

First of all, if you want a list or all symbols try:

Symbol.all_symbols

Next, if you want to define a method on the class object itself (i.e.
a class method) the you should try this:

class Symbol
  def Symbol.my_new(name)
    ...
  end
end

Symbol.my_new('foo')

Now, lastly, you should note that new has no implementation on Symbol.
This is deliberate. If you want to create a symbol from a string you
should use the String#to_sym method:

class Symbol
  def Symbol.my_new(name)
    name.to_sym
  end
end

If you want to get into the details of why all this is the way it is,
then please ask. If you want to name my_new to new go ahead but I
wouldn't count on it being called for symbols being created in literal
style or via String#to_sym.

Brian.