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Re: [vox-tech] Perl: Checking if a hash exists and is true
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Re: [vox-tech] Perl: Checking if a hash exists and is true



On Mon, Jul 09, 2001 at 02:39:15PM -0500, Jay Strauss wrote:
> I'm trying to check if a hash key exists and if the value is 1.  I'm passing
> the reference to the hash to a subroutine like:
> 
> my $help = 1;
> my %hash = (help=>\$help);
> somefunc(\%hash);
> 
> sub somefunc {
>     my ($refHash) = @_;
> 
>     if ((defined $refHash->{help}&& ${$refHash->{help}}) {
>         # stuff
>     }
>     else {
>         # other stuff
>     }
> }
> 
> This seems long an clumsy, I suspect there is a cleaner way to do it in perl
> but I don't know how.  I played around with "exists" but that just tells me
> that the value exists.  I need to do some processing if the value is "1" and
> other processing for "0";

This is pretty much how you have to do it, I'm afraid.

If you were using 'use strict', however, the 'help' bareword would not
be accepted.  I probably would swap 'exists' for 'defined', unless you
might actually set $refHash->{'help'} to undef explicitly, and want to
test for that (but that's just me); also, the ${$refHash->{help}}
could be shortened to $refHash->{'help'}.

So, if you care, here's my version - but it doesn't solve the
"problem" which caused you to ask in the first place :(

sub somefunc {
  my $refHash = shift;

  if (exists $refHash->{'help'} && $refHash->{'help'}) {
    # stuff
  } else {
    # other stuff
  }
}

The difference is pretty much all style, so feel free to ignore it
(except, I really do recommend you use 'use strict').

Micah


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