Re: Perl Inheritance & module variables

So, you have a module called Foo::Bar and objects of the class Foo::Bar, and you want to find the version of the module associated with the object, yes ? For example, while doing some superclass stuff ?

Which would be something along the lines:

  package Foo::Bar ;
  .....
  our $VERSION = "0.00" ;
  .....
[download]

and somewhere you have:

  my $obj = new Foo::Bar (...) ;
[download]

and somewhere else you want to find the $VERSION associated with $obj ?

Suppose you had Foo/Bar.pm:

  package Foo::Bar ;

  use strict ; use warnings ;

  our $VERSION = "1.01" ;

  use base qw(Foo);

  sub new { return bless [], shift ; } ;

  1 ;
[download]

and Foo.pm:

  package Foo ;

  use strict ; use warnings ;

  our $VERSION = "0.11" ;

  sub version {
    my ($self) = @_ ;
    no strict 'refs' ;                  # NB: seatbelt off.
    return ${ref($self)."::VERSION"} ;  # "Symbolic Reference"
  } ;

  1 ;
[download]

Then:

  use strict ; use warnings ;

  use Foo::Bar ;

  my $obj = new Foo::Bar ;

  print $obj->version(), "\n" ;
[download]

should print:

  1.01
[download]

which may have been what you had in mind.

It may also be what kyle just recommended NOT to do ?

Comment on Re: Perl Inheritance & module variables Select or Download Code

Replies are listed 'Best First'.
Re^2: Perl Inheritance & module variables by diabelek (Beadle) on Sep 19, 2008 at 16:26 UTC
Well that does what I want but I really hate having to turn off the strict refs... I think I would prefer to just copy the data into the instance and deal it with that way unless there is a lot of data i need to copy or its time sensitive. Unless there is a better way of doing it, I think I might just keep that in my back pocket for when I really do need it. Thanks a bunch	[reply]
Re^3: Perl Inheritance & module variables by gone2015 (Deacon) on Sep 20, 2008 at 08:53 UTC
Wishing to maintain "strict refs purity" is entirely commendable :-) For completeness, however, I'll point out that the 'no strict'-ness is scoped within the current block. So the unpleasantness is contained. In the code I gave the the nastiness was enclosed in a subroutine. If it's necessary to do this in 'open code' you can always: `{ no strict 'refs' ; .... # unspeakable stuff redacted } ;` [download] to avoid contagion Anyway, I think that with a small penance, in the form, say, of an explanatory comment, one can forgive oneself this particular sin -- provided it doesn't become a habit :-)	[reply] [d/l]