From: Yohanes Santoso <ysantoso@...>
Date: 2002-02-22T19:59:48+09:00
Subject: Re: recursive require

Ron Jeffries <ronjeffries@REMOVEacm.org> writes:
> On 21 Feb 2002 16:02:35 -0800, Yohanes Santoso
> <ysantoso@jenny-gnome.dyndns.org> wrote:
> 
> >2. Use forward declaration
> >test.rb:
> >class Code end
> >Code.something()
> >
> >Personally, I like solution #2 because it's easy and fast. I put all
> >the forward declarations in a separate file which is 'require'd by
> >both code.rb and test.rb.
> 
> Thanks for answering, but I'm araid I don't understand this idea. If
> test.rb doesn't require code.rb, how does this work? If the two files
> don't require each other, how can I run either one and get the tests to
> run (which is what I'm trying to accomplish)?
> 

Here are three files, abc.rb, xyz.rb, and global.rb. abc contains
class Abc, and xyz contains class Xyz. Abc and Xyz are
inter-dependant.  Putting "require 'xyz'" in abc.rb and "require
'abc'" in xyz.rb will not work as you pointed out.

So, pre-declare class Abc in xyz.rb and pre-declare class Xyz in
abc.rb. However, rather than putting the declaration everywhere,
collect them into a file: global.rb.

Then, from abc.rb and xyz.rb require global.rb


global.rb:
class Abc 
end
class Xyz 
end

abc.rb:
require 'global'
class Abc
  def Abc.name
    "abc"
  end
  def whoami
    puts "abc knows xyz:"
    puts Xyz.name
    puts "abc tells the truth"
  end
end
a = Abc.new
a.whoami

xyz.rb:
require 'global'
class Xyz
  def Xyz.name 
    "xyz"
  end
  def whoami
    puts "xyz knows abc:"
    puts Abc.name
    puts "xyz tells the truth"
  end
end
x = Xyz.new
x.whoami


jenny:~/tmp> ruby abc.rb
abc knows xyz:
Xyz
abc tells the truth
jenny:~/tmp> ruby xyz.rb
xyz knows abc:
Abc
xyz tells the truth