[Buffalo-pm] Test if module is loaded

[Gianni, Andrew]

Kevin is correct, in that you don't really need to worry about checking, as use and require do that for you. That said, the easiest way to check for a loaded package is to simply check for the definedness of %That::Package:: (not the extra set of ::). For example:

eval 'require That::Package' unless eval 'defined %That::Package::';
die $@ if $@ # check for eval error

if you dump %That::Package::, you'll see that it shows you all of the available data structures and methods/functions for that package space *if* it has already been required/used.

Andrew

> -----Original Message-----
> From: buffalo-pm-bounces+agianni=buffalo.edu at pm.org [mailto:buffalo-pm-
> bounces+agianni=buffalo.edu at pm.org] On Behalf Of Eye, Kevin
> Sent: Tuesday, December 08, 2009 1:08 PM
> To: Joshua Johnson
> Cc: Buffalo Perl Mongers
> Subject: Re: [Buffalo-pm] Test if module is loaded
> 
> All the "use" statements execute as the script is being read (compiled)
> and it won't actually run the code in them a second time. It's
> basically already doing the "if" statement you're trying to write.
> "require" is the same way -- it will only load/run it once (though at
> run-time). You need to use "do" to actually run a file more than once.
> You could verify all of this with a few test files and some print
> statements.
> 
> If you do really need to see if something has already been loaded you
> can look in the global/special variable %INC. To see if My::Module is
> loaded, check to see if $INC{'My/Module.pm'} is defined. Not sure why
> it is all translated that way (the /'s and :'s). Might be documented
> here: http://perldoc.perl.org/perlvar.html
> 
>  - Kevin
> 
> 
> 
> 
> On Dec 8, 2009, at 12:53 PM, Joshua Johnson wrote:
> 
> > Hello all!
> >
> > Is there a way to test if a perl module is loaded? I'm working on a
> > small project where I load some modules dynamically as part of a
> > configuration and then "use" them at that time. I don't get any
> errors
> > but I just feel dirty loading a module that may have already been
> > loaded. So, if at the top of the file I do:
> >
> > use Whatever::Project::MyStuff;
> >
> > Can I find out later if Whatever::Project::MyStuff is already loaded?
> > I suppose it may not matter or have any kind of performance impact
> but
> > now I'm just curious to know if it can be done.
> >
> > Thanks,
> > Josh J
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