From: Jeremy Henty <jeremy@...>
Date: 2006-11-02T20:30:15+09:00
Subject: Re: variable pointer

On 2006-11-01, dblack@wobblini.net <dblack@wobblini.net> wrote:

> Here's an example from a program which models Ideas; each Idea belongs
> to a Page.
>
>>> i = Idea.find(6)
>=> #<Idea:0xb79eec2c @attributes={"page_id"=>"6", "id"=>"6",
> "content"=>"Go to Paris"}>
>
> # Save the idea's page in p
>>> p = i.page
>=> #<Page:0xb79e4a88 @attributes={"scratchpad_id"=>"6",
> "title"=>"Domestic travel", "id"=>"6"}>
>
> # Change the idea's page to a different one
>>> i.page = Page.find(7)
>=> #<Page:0xb79d1b18 @attributes={"scratchpad_id"=>"1",
> "title"=>"Foreign travel", "id"=>"7"}>
>
> # Examine the saved page -- it's the new one
>>> p
>=> #<Page:0xb79d1b18 @attributes={"scratchpad_id"=>"1",
> "title"=>"Foreign travel", "id"=>"7"}>

Yikes!  How is this even possible?  Somehow the method is changing the
variable bindings in its caller.  Is this related to Binding.of_caller
(which exploited a bug in 1.8.4 and broke when the bug was fixed in
1.8.5 - see
<URL:http://eigenclass.org/hiki.rb?breakpoint+breaking+in+1.8.5>)?

Jeremy Henty