From: Charles Oliver Nutter <headius@...>
Date: 2010-04-30T11:36:18+09:00
Subject: Re: Use of STDOUT.flush after puts

On Thu, Apr 29, 2010 at 4:24 PM, Caleb Clausen <vikkous@gmail.com> wrote:
> On 4/29/10, hemant <gethemant@gmail.com> wrote:
>> How can reopen change the class btw? Ruby is not a class oriented language
>> btw.
>
> Check out this code. No other method in all of ruby has this behavior.
>
>  p $stderr.class #=>IO
>
>  f=File.new "foo","w"
>  $stderr.reopen(f)
>
>  p $stderr.class #=>File

This is a really nasty feature not a lot of people know about. It's
not possible for us to support in JRuby because the underlying object
can't actually change class:

~/projects/jruby ➔ jruby -rjruby -e 'p JRuby.reference($stdout).class'
Java::OrgJruby::RubyIO

~/projects/jruby ➔ jruby -rjruby -e 'p
JRuby.reference(File.open("build.xml")).class'
Java::OrgJruby::RubyFile

Arbitrary IO objects are org.jruby.RubyIO objects behind the scenes,
while files are RubyFile (< RubyIO) and sockets are RubySocket (<
RubyIO) or one of its subclasses. "Becoming" another class isn't an
option.

The closest we could probably come would be to change the .class to a
common superclass of both actual types, but that's still pretty goofy.

I'm of the opinion that .reopen should be discouraged in general.

- Charlie