From: Julian Snitow <vangczung@...>
Date: 2003-05-27T15:24:34+09:00
Subject: Re: Constant Definitions and Hiding

On Mon, 26 May 2003 21:58:48 +0200, Robert wrote:

> 
> Hi,
> 
> we had a discussion on #irc the minute before and I'm thinking that there
> ought to be a warning in this situation:
> 
> class Foo
>   BAR = "bar"
> 
>   def print_it
>     p BAR
>   end
> end
> 
> class Bar < Foo
>   def print_it
>     p BAR
>   end
> end
> 
> Foo.new.print_it
> Bar.new.print_it
> 
> class Bar < Foo
>   # next line should IMHO issue a warning
>   # because of the hidden constant Foo::BAR
>   BAR = "foo"
> end
> 
> Foo.new.print_it
> Bar.new.print_it
> 
> Output:
> 
> "bar"
> "bar"
> "bar"
> "foo"
> 
> This code does not warn (at least with 1.6.8) either with or without -w.
> 
> What do others think?
> 
>     robert

Perhaps using constants inside a class is what ought to be warned.

class Foo
  def bar
    "bar"
  end
  def print_it
    p bar
  end
end

class Bar < Foo
  def bar
   "foo"
  end
end

In a language that lets you do such beautiful, fluid things with
functions, the C++ mindset can only hold you back. ;-)

If you must distrust the programmer so much, you can either make bar a
class method  ( def Foo.bar ), and def print_it; p Foo.bar; end,  or, if
going the constant route, refer to Foo::BAR explicitly.   If you don't
specify that you only want the BAR defined in class Foo, and not some
subclass's idea of BAR, then the example you posted shows the correct
behavior on the part of the ruby interpreter.

Remember the line, "A computer never does what you want it to do; only what you
tell it."?   No amount of warnings will change that.  :-)

Cheers,
Julian