From: Shadowfirebird <shadowfirebird@...>
Date: 2008-07-23T22:48:13+09:00
Subject: Re: circular 'require'

I found a very easy way around it.  This is what bothers me.  If it's
that easy, why doesn't require do it?

# test1.rb
$" << "test1.rb"
load("test2.rb") unless $".include?("test2.rb")
class One < Two
   def self.testone(); Two.whoistwo; end
   def self.whoisone();  puts "class one"; end
end

# test2.rb
$" << "test2.rb"
load("test1.rb") unless $".include?("test1.rb")
class Two
   def self.testtwo(); One.whoisone; end
   def self.whoistwo(); puts "class two"; end
end


On Wed, Jul 23, 2008 at 2:03 PM, Michael T. Richter
<ttmrichter@gmail.com> wrote:
> On Wed, 2008-07-23 at 20:39 +0900, Calamitas wrote:
>
>> test1.rb is executed twice, but what probably caused the error in the
>> OP's original program (the OP pared it down to a point where it
>> actually did "work") is the fact that "the rest of test1.rb" is
>> executed before "the rest of test2.rb". It can probably be solved by
>> doing "ruby -r test1.rb" instead, but that's icky. Generally, if I
>> *were* to use circular requires, I'd never put "executable code" in
>> either file, just "declarations". I don't use them though. Not anymore
>> after I've been bitten a few times.
>
>
> Here's what the OP was talking about, I suspect, taken down to its
> briefest possible example:
>
>
>        $ cat test1.rb
>        require 'test2'
>        class NeededInTest2
>          @@funny_stuff = NeededInTest1.new
>        end
>
>        michael@isolde:~/junk$ cat test2.rb
>        require 'test1'
>        class NeededInTest1
>          @@funny_stuff = NeededInTest2.new
>        end
>
>        michael@isolde:~/junk$ ruby test1.rb
>        ./test1.rb:3: uninitialized constant NeededInTest2::NeededInTest1 (NameError)
>                from /home/michael/software/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require'
>                from /home/michael/software/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'
>                from ./test2.rb:1
>                from /home/michael/software/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require'
>                from /home/michael/software/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'
>                from test1.rb:1
>
>
> This is the problem boiled down to its essence.  There is no easy way
> out of this either that doesn't either a) mangle the architecture or b)
> fail.  You can't use something like C/++'s "include guards" to get
> around this, nor can you use any kind of super-class elevation trick or
> the like.  What would be needed to solve this issue would be for ruby to
> have a proper sense of modules and do linkage across those instead of
> treating the entire tree of requires as, in effect, one ginormous text
> file.
>
> --
> Michael T. Richter <ttmrichter@gmail.com> (GoogleTalk:
> ttmrichter@gmail.com)
> Theory is knowledge that doesn't work. Practice is when everything works
> and you don't know why. (Hermann Hesse)
>



-- 
Me, I imagine places that I have never seen / The colored lights in
fountains, blue and green / And I imagine places that I will never go
/ Behind these clouds that hang here dark and low
But it's there when I'm holding you / There when I'm sleeping too /
There when there's nothing left of me / Hanging out behind the
burned-out factories / Out of reach but leading me / Into the
beautiful sea