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Re: disambiguating require (or: require loves join more than catfile)

by Monk::Thomas (Beadle)
on Jul 23, 2013 at 15:09 UTC ( #1045892=note: print w/ replies, xml ) Need Help??


in reply to disambiguating require (or: require loves join more than catfile)

Are you ~sure~ this does what you want it to? Require behaves differently if you feed it a bareword or a variable. (Maybe this was the reason for catfile?)

http://perldoc.perl.org/functions/require.html

use strict; use warnings; my $x="x"; my $module = $x . '::' . $x; print "$module\n"; eval { require $module; };
The eval block needs some finetuning to actually do what you want it to. (Do something if require succeeds, do something else if require fails. Recommendation: Use Try::Tiny and stop worrying about all the ways eval / $! / $_ can go wrong.
use strict; use warnings; use Try::Tiny; my $x="x"; my $module = $x . '::' . $x; try { require $module; print "Found module $module.\n"; } catch { print "Failed to find module $module!\n"; };


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Re^2: disambiguating require (or: require loves join more than catfile)
by rovf (Priest) on Jul 23, 2013 at 15:37 UTC
    Are you ~sure~ this does what you want it to?
    I think so. I have the absolute path to a file containing a set of functions which I want to drag into my code, and this should happen at runtime. If there is a problem with the 'required' file, it's fine for me to get an exception. I *could* catch it, but in my particular case I just want to abort the program, so the default behaviour is fine.


    -- 
    Ronald Fischer <ynnor@mm.st>
      Ah. Then another question: Do you expect this code to run on multiple platforms? (I'm asking because you used catfile.) In that case I'd recommend using Path::Class in favor of File::Spec because

      The well-known module File::Spec also provides this service, but it's sort of awkward to use well, so people sometimes avoid it, or use it in a way that won't actually work properly on platforms significantly different than the ones they've tested their code on.

      In fact, Path::Class uses File::Spec internally, wrapping all the unsightly details so you can concentrate on your application code. Whereas File::Spec provides functions for some common path manipulations, Path::Class provides an object-oriented model of the world of path specifications and their underlying semantics. File::Spec doesn't create any objects, and its classes represent the different ways in which paths must be manipulated on various platforms (not a very intuitive concept). Path::Class creates objects representing files and directories, and provides methods that relate them to each other.

      -- from http://search.cpan.org/~kwilliams/Path-Class-0.32/README.pod

      Recommended reading: http://www.perladvent.org/2012/2012-12-01.html

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