Re: Re: Check to see if a variable exists

One way I have done config files is to setup the config file as a do'able variable in itself that is a reference to a hash.. You can also use Data::Dumper to create the file. config.txt file as such:

$config = \{
            'Variable1' => 'variable value',
            'Variable2' => ['a','b','c'],
           };
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Then you can:

do "config.txt" or die "$! $@";
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This creates a variable $config that is a reference to a hash containing all your configuration variables. If your passing the configuration to subroutines you can just pass $config and your subroutine has access to all the config variables and you saved some overhead.

Granted you have to dereference the hash, but references are a good thing to learn..

if (exists $config->{Variable1}) {}
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Re: Re: Re: Check to see if a variable exists by hardburn (Abbot) on Nov 13, 2003 at 20:08 UTC
Even better is to put your config in a module, with each configuration option being a subroutine declared with an empty prototype (and thus considered by the compiler for inlineing). Example: `package My::Config; sub VARIABLE1 () { 'variable value' } sub VARIABLE2 () { [ 'a', 'b', 'c' ] } 1;` [download] You call it like this: `use My::Config; my $var1 = My::Config::VARIABLE1;` [download] Which, if you put this through B::Deparse, will look like: `use My::Config; # Actually, my $var = 'variable value';` [download] And is thus gives you the advantages of a hard-coded variable without the icky problem of maintainability. Note, though, that `strict` won't catch undeclared variables with full package names, so if you do: `my $var1 = My::Config::VAR1;` [download] `strict` will happily allow it. ---- I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident. -- Schemer `: () { :\|:& };:` Note: All code is untested, unless otherwise stated	[reply] [d/l] [select]

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Re: Re: Re: Check to see if a variable exists
by hardburn (Abbot) on Nov 13, 2003 at 20:08 UTC

Even better is to put your config in a module, with each configuration option being a subroutine declared with an empty prototype (and thus considered by the compiler for inlineing). Example:

package My::Config;

sub VARIABLE1 () { 'variable value' }
sub VARIABLE2 () { [ 'a', 'b', 'c' ] }

1;
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You call it like this:

use My::Config;
my $var1 = My::Config::VARIABLE1;
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Which, if you put this through B::Deparse, will look like:

use My::Config;   # Actually, 
my $var = 'variable value';
[download]

And is thus gives you the advantages of a hard-coded variable without the icky problem of maintainability.

Note, though, that strict won't catch undeclared variables with full package names, so if you do:

my $var1 = My::Config::VAR1;
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strict will happily allow it.

----
I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

: () { :|:& };:

Note: All code is untested, unless otherwise stated

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