From: "Michael T. Richter" <ttmrichter@...>
Date: 2008-07-23T23:39:02+09:00
Subject: Re: circular 'require'

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On Wed, 2008-07-23 at 22:48 +0900, Shadowfirebird wrote:

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



Try my code with that:


        michael@isolde:~/junk$ cat test1.rb
        $" << "test1.rb"
        load("test2.rb") unless $".include?("test2.rb")
        class NeededInTest2
          @@funny_stuff = NeededInTest1.new
        end
        
        michael@isolde:~/junk$ cat test2.rb
        $" << "test2.rb"
        load("test1.rb") unless $".include?("test1.rb")
        class NeededInTest1
          @@funny_stuff = NeededInTest2.new
        end
        
        michael@isolde:~/junk$ ruby test1.rb
        ./test2.rb:4: uninitialized constant NeededInTest1::NeededInTest2 (NameError)
        	from test1.rb:2:in `load'
        	from test1.rb:2


The real solution remains a proper system of modules in Ruby.


> # 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)
> >
> 
> 
> 

-- 
Michael T. Richter <ttmrichter@gmail.com> (GoogleTalk:
ttmrichter@gmail.com)
It's OK to figure out murder mysteries, but you shouldn't need to figure
out code. You should be able to read it. (Steve McConnell)

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