From: Calamitas <calamitates@...>
Date: 2008-07-23T20:39:42+09:00
Subject: Re: circular 'require'

On Wed, Jul 23, 2008 at 12:18 PM, Stefano Crocco
<stefano.crocco@alice.it> wrote:
> On Wednesday 23 July 2008, Shadowfirebird wrote:
>> >ruby -w test1.rb
>>
>> ./test1.rb:4: unititialized constant Two (NameError)
>
> require 'test1.rb'
>
> is executed:
>
> * the file test1.rb is read and parsed
> * starts the execution of test1.rb
> * the line require 'test2.rb' is executed. This means:
>  * the file test2.rb is read and parsed
>  * starts the execution of test2.rb
>  * the line require 'test1.rb' is executed. This means:
>    * the file test1.rb is read and parsed
>    * starts the execution of test1.rb
>    * the line require 'test2.rb' is executed. This means:
>      ...

Actually, I'm neither seeing the error the OP got, neither the endless
loop you seem to get. Looks like a file that is required gets added to
$" before its contents is executed, and that a file passed on the
command line -- like the OP did, so not using the -r switch -- is not.
So basically the execution is as follows:

  * the file test1.rb is read and parsed
  * starts the execution of test1.rb
  * the line require 'test2.rb' is executed. This means:
    * the file test2.rb is read and parsed
    * adds "test2.rb" to $"
    * the line require 'test1.rb' is executed. This means:
      * the file test1.rb is read and parsed
      * adds "test1.rb" to $"
      * the line require 'test1.rb' is executed. Does nothing as
"test1.rb" is in $"
      * The rest of test1.rb is executed
    * The rest of test2.rb is executed
  * The rest of test2.rb is executed again

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.

Peter