On Aug 28, 11:16 pm, [EMAIL PROTECTED] (Phil) wrote:
> Ok so here's the deal...I have the following:
>
> $var = 123;
>
> GetOptions( 'v|var=n' => \$var);
>
> %xyz = (
> type1 => { ABC => "after zero comes $var", },
> type2 => {...etc.},
> );
>
> get_var() if $condition;
>
> sub get_var {
> $var = `external gui app to get input from user`;
> chomp($var);
>
> }
>
> print "$xyz{type1}{ABC}\n";
>
> All looks good and well, but $var in %xyz retains it's original value
> while the global variable $var gets changed to lets say 456, which is
> a moot point since we're not printing $var, we're printing the hash
> value.. I've tried declaring the subroutine before the hash, but it's
> not really feasible considering the application, nor did it change the
> outcome when I tried. Using the command line option --var=456
> obviously changes the variable before %xyz is even interpreted. So my
> question is (as the title states)...how do I modify a variable in a
> global hash value after the hash has been declared? Keep in mind that
> the key ABC => "etc.." must remain there since $condition won't always
> exist, and since the option to modify it with --var also won't exist
> when $condition is met.
The problem is that the *variable* is NOT stored in that hash. Only
its value at the time of the initialization is stored. When you
interpolate a variable into a double quoted string, Perl simply takes
the current value of that variable and puts it into the string. There
is no link of any kind between the string and the original variable
from whence the value came.
Here's one possible solution: store a reference to a subroutine that
returns a certain string, rather than the string itself:
%xyz = (
type1 => { ABC => sub { "after zero comes $var", },
type2 => {...etc.},
);
And then when you want to print the value, call the subroutine:
print $xyz{type1}{ABC}->(), "\n";
Here's a short-but-complete script that demonstrates this solution:
#!/usr/bin/perl
use strict;
use warnings;
my $var = '123';
my %xyz = (
type1 => { ABC => sub { "value: $var" } }
);
print "Before mod: ", $xyz{type1}{ABC}->(), "\n";
$var = '456';
print "After mod: ", $xyz{type1}{ABC}->(), "\n";
__END__
Output:
Before mod: value: 123
After mod: value: 456
Hope this helps,
Paul Lalli
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