Rails - Jul 2009 - Curious why copying an array element by element fails when using strip!

Hi,

I wanted to copy one array into another, element by element, so that I
could edit the source data as necessary.  I simultaneously changed a
source element using "strip!".  The latter step corrupted the
copying.  Without the bang operator,  all works as expected.

The above question, source code and output are stored at
http://www.pastie.org/539430.

This is not an earth-shattering problem.  I''m just curious why it
doesn''t work ... especially because it took me a good while to figure
out the cause of my app''s failure.

Thanks in Advance,
Richard

Hi,

Did you read the documentation on strip and strip!?  
(http://ruby-doc.org/core/classes/String.html#M000820)

strip! modifies the existing string (returning itself if a modification  
occurred and nil if nothing was done), while strip does the modification  
and returns a new string.

Simon


On Thu, 09 Jul 2009 08:11:30 +0800, RichardOnRails  
<RichardDummyMailbox58407-gP6xRNRnnqSxhq/XJNNIW0EOCMrvLtNR@public.gmane.org>
wrote:
>
> Hi,
>
> I wanted to copy one array into another, element by element, so that I
> could edit the source data as necessary.  I simultaneously changed a
> source element using "strip!".  The latter step corrupted the
> copying.  Without the bang operator,  all works as expected.
>
> The above question, source code and output are stored at
> http://www.pastie.org/539430.
>
> This is not an earth-shattering problem.  I''m just curious why it
> doesn''t work ... especially because it took me a good while to
figure
> out the cause of my app''s failure.
>
> Thanks in Advance,
> Richard
>

The strip! method isn''t corrupting the copy.  It''s that the
strip!
method returns nil if nothing was stripped from the string.  That''s
why you are getting nil for the second array element in the copy.

Jamey


On Wed, Jul 8, 2009 at 8:11 PM,
RichardOnRails<RichardDummyMailbox58407-gP6xRNRnnqSxhq/XJNNIW0EOCMrvLtNR@public.gmane.org>
wrote:
>
> Hi,
>
> I wanted to copy one array into another, element by element, so that I
> could edit the source data as necessary.  I simultaneously changed a
> source element using "strip!".  The latter step corrupted the
> copying.  Without the bang operator,  all works as expected.
>
> The above question, source code and output are stored at
> http://www.pastie.org/539430.
>
> This is not an earth-shattering problem.  I''m just curious why it
> doesn''t work ... especially because it took me a good while to
figure
> out the cause of my app''s failure.
>
> Thanks in Advance,
> Richard
> >
>
>

Hi Simon  & Jamey,

I forgot the first commandment of programming: RTFM.  Sorry, guys.
Thanks for you excellent responses.

Best wishes,
Richard

On Jul 8, 8:11 pm, RichardOnRails
<RichardDummyMailbox58...-FtJgd9dCuO3JTKoYRCtP1UEOCMrvLtNR@public.gmane.org>
wrote:
> Hi,
>
> I wanted to copy one array into another, element by element, so that I
> could edit the source data as necessary.  I simultaneously changed a
> source element using "strip!".  The latter step corrupted the
> copying.  Without the bang operator,  all works as expected.
>
> The above question, source code and output are stored
athttp://www.pastie.org/539430.
>
> This is not an earth-shattering problem.  I''m just curious why it
> doesn''t work ... especially because it took me a good while to
figure
> out the cause of my app''s failure.
>
> Thanks in Advance,
> Richard