From: Okushi <okushi@...>
Date: 2007-07-26T05:28:04+09:00
Subject: Re: Question - Passing parameters by reference

I think it's the clearest explanation so far Jason.

I believe it's a good practice to stop thinking in terms of pointers
and start thinking in terms of objects.
You don't pass a variable by reference, you pass an object.

With a little time you'll find this approach a lot more comfortable.

Cheers !

On 25/07/07, Jason Roelofs <jameskilton@gmail.com> wrote:
> You're pretty close, just some details as to the whyness:
>
> String are of course instances of the String class. This is simply an array
> of characters, of which you can modify freely, as you've discovered.
>
> Numbers, on the other hand are special case instances of FixNum, BigNumber,
> any subclass of Numeric. These have no underlying data representation, they
> *are* the number they represent. So if you tried to do the same to Fixnums
> like you can with String, you'd actually be trying to change 1 to equal 2,
> and you can imagine what kind of havok that would cause.
>
> So with Strings, you have an underlying character array you can play with,
> but with Numerics you have to change the number your variable is pointing
> to.
>
> Hopefully I made that understandable, though please correct me if something
> I said was wrong.
>
> Jason
>
> On 7/25/07, caof2005 <caof2005@gmail.com> wrote:
> >
> > Thanks for the response, although I was just wondering that using
> > Strings as a parameters in a method definition is a special case.
> > Let me explain....
> >     I observed that when you use a string as a parameter in a method
> > definition, it can be changed by applying several operations inside
> > the method, for instance you can change it, by adding letters to the
> > string, changing the content to uppercase etc.
> > So I figured out that when you use a string, what really happens
> > inside the method is that you don't create a new object, you just use
> > the reference.
> >     In opposition as if you use other kind of parameters in a method
> > definition, let say for example an int variable.
> >     If you try to change this int variable inside the method, it
> > simply doesn't work, what happens is that you get a "copy" of the
> > object that you're passing but after the  method is finished, that
> > copy disappears and at the end the parameter that you passed was not
> > affected.
> > Am I correct with my conclusions?
> >
> > Regards
> > Carlos
> >
> > On Jul 25, 11:35 am, dbl...@wobblini.net wrote:
> > > Hi --
> > >
> > > On Thu, 26 Jul 2007, Chris Thiel wrote:
> > > > What if the method is returning something else already and you don't
> > want
> > > > to have to return the changed value? How do you pass in a variable to
> > a
> > > > method and have the change stick when it exists the method in ruby?
> > >
> > > You can change an object:
> > >
> > >    def change_me(str)
> > >      str.upcase!
> > >    end
> > >
> > >    s = "abc"
> > >    change_me(str)
> > >    puts s          # ABC
> > >
> > > But you can't change the bindings.  In the example, I've got s and str
> > > both containing references to the same string.  But the names of the
> > > identifiers themselves, s and str, are solely the business of their
> > > local scopes, which are different as between the method body and the
> > > calling context.
> > >
> > > David
> > >
> > > --
> > > * Books:
> > >    RAILS ROUTING (new!http://www.awprofessional.com/title/0321509242)
> > >    RUBY FOR RAILS (http://www.manning.com/black)
> > > * Ruby/Rails training
> > >      & consulting:  Ruby Power and Light, LLC (http://www.rubypal.com)
> >
> >
> >
> >
>


-- 
Rusty
http://www.oxidized.com.ar/
okushi@gmail.com