Dynamic finding of missing constants


#1

Hi.

I’m doing some slightly interesting things with Ruby, and I wanted to
know
of there’s a language way of interrupting the process for finding a
Constant name, like the method_missing method. The closest thing I’ve
been
able to work out is to rescue the NameError at some toplevel, but this
is
not transparent enough for me. Anyone have good any good suggestions?

Regards
Ola B.


#2

On Nov 25, 2005, at 10:22 AM, Ola B. wrote:

Hi.

I’m doing some slightly interesting things with Ruby, and I wanted
to know of there’s a language way of interrupting the process for
finding a Constant name, like the method_missing method.

Yep, const_missing().

James Edward G. II


#3

“O” == Ola B. removed_email_address@domain.invalid writes:

O> I’m doing some slightly interesting things with Ruby, and I wanted to
know
O> of there’s a language way of interrupting the process for finding a
O> Constant name, like the method_missing method.

You have Module#const_missing

moulon% ri Module#const_missing
--------------------------------------------------- Module#const_missing
mod.const_missing(sym) => obj

 Invoked when a reference is made to an undefined constant in _mod_.
 It is passed a symbol for the undefined constant, and returns a
 value to be used for that constant. The following code is a (very
 bad) example: if reference is made to an undefined constant, it
 attempts to load a file whose name is the lowercase version of the
 constant (thus class +Fred+ is assumed to be in file +fred.rb+). If
 found, it returns the value of the loaded class. It therefore
 implements a perverse kind of autoload facility.

   def Object.const_missing(name)
     @looked_for ||= {}
     str_name = name.to_s
     raise "Class not found: #{name}" if @looked_for[str_name]
     @looked_for[str_name] = 1
     file = str_name.downcase
     require file
     klass = const_get(name)
     return klass if klass
     raise "Class not found: #{name}"
   end

moulon%

Guy Decoux


#4

At 17:28 2005-11-25, you wrote:

James Edward G. II
Ah, sorry. Thanks for the pointer. I thought I checked for it. But
apparently my brain is fried after to much friday-work.

/O