From: RichardOnRails <RichardDummyMailbox58407@...>
Date: 2009-10-26T22:45:13+09:00
Subject: Re: Given a String instance, how to create a different but equivalent 	one

On Oct 26, 1:13 am, Rajinder Yadav <devguy...@gmail.com> wrote:
> RichardOnRails wrote:
> > Given a String instance,  how to create a different but equivalent one
>
> > The code below shows the incorrect way and two correct ways
> > to create a second string instance that equal to a given string
> > instance.
>
> > Q1: Are there better ways to do this than the two I concocted?
> > Q2: How can I create a proc to invoke it with each of my candidate
> > assignment statements
>
> > I am interest in this issue because I made the naive assignment in a
> > project I am working on and
> > had to waste time trying debugging it.
>
> > Thanks in advance,
> > Richard
>
> > # Version 1: Wrong!
>
> > os = "abc"               # Original String
> > ws = os            # Thinking ws can be modified independently of os.
> > 3.times { ws << (ws[-1] + 1).chr; puts ws }
> > while ws.size > os.size
> >   ws.chop; puts ws
> > end
>
> > # Version 2: OK
>
> > puts
> > os = "abc"                               # Original String
> > ws = String.new(os)                # ws is a reference to a different string
> > oobject than os but initially equal to os
> > 3.times { ws << (ws[-1] + 1).chr; puts ws }
> > while ws.size > os.size
> >   ws.chop!; puts ws
> > end
>
> > # Version 3: OK
>
> > puts
> > os = "abc"                               # Original String
> > ws = os + ""                     # A less verbose way to get a new string object
> > initially equal to os
> > 3.times { ws << (ws[-1] + 1).chr; puts ws }
> > while ws.size > os.size
> >   ws.chop!; puts ws
> > end
>
> Use String.dup to create a copy
>
> irb(main):050:0> s1='hello'
> => "hello"
> irb(main):050:0> s2=s1
> => "hello"
> irb(main):049:0> s1.eql? s2
> => true
> irb(main):048:0> s1.equal? s2
> => true
>
> irb(main):047:0> s3=s1.dup
> => "hello"
> irb(main):046:0> s3
> => "hello"
> irb(main):045:0> s3.eql? s1
> => true
> irb(main):044:0> s3.equal? s1
> => false
>
> --
> Kind Regards,
> Rajinder Yadav
>
> http://DevMentor.org
>
> Do Good! - Share Freely, Enrich and Empower people to Transform their lives.

Hi Rajinder ,

> Use String.dup to create a copy

Thanks.  I "knew" there was a "right way" in Ruby.

Best wishes,
Richard