1: ####################################################################
   2: #  sub
   3: #       testFunction
   4: #
   5: #  purpose
   6: #       takes a module name and function name, returns true if the
   7: #       function exists in the module
   8: #	
   9: #  syntax: testFunction("Mine::Module", "myFunction");
  10: #
  11: sub testFunction {
  12:     my ($modname, $funcname) = @_;
  13:    
  14:     my $pkgname = $modname.".pm";
  15:     $pkgname =~ s/\:\:/\//g; #this is UNIX Specific
  16: 
  17:     #we use eval to avoid requiring a pkg which doesn't exist
  18:     eval '
  19:         no strict;
  20:         require($pkgname);
  21:         local *stash = *{ "${modname}::" };
  22: 
  23:         return unless defined &{ $stash{$funcname} };
  24:         1;
  25:         ';
  26: }

Replies are listed 'Best First'.
RE: testFunction
by johannz (Hermit) on Mar 23, 2000 at 23:05 UTC
    Perl already provides a built-in function to do this. It is the 'can' function which in contained in the UNIVERSAL package which every module inherits from. From the Advanced Perl Programming Book(O'Rielly): 
    Chapter 7.3 UNIVERSAL

All modules implicitly inherit from a built-in module
called UNIVERSAL and inherit the following three methods:

isa (package name)

     For example, Rectangle->isa('Shape') returns true if
the Rectangle module inherits (however indirectly) from
the Shape module. 
 
can (function name)
 
     Rectangle->can('draw') returns true if the Rectangle
or any of its base packages contain a function called draw. 
 
VERSION (need version)
 
      If you say, 

          package Bank;
          $VERSION = 5.1;
 
      and the user of this module says,
 
          use Bank 5.2;

      Perl automatically calls Bank->VERSION(5.2), which
can, for instance, make sure that all libraries required
for version 5.2 are loaded. The default VERSION method
provided by UNIVERSAL simply dies if the Bank's $VERSION
variable has a lower value than that needed by the user of
the module.
 
Because Perl allows a package to shamelessly trample on
other namespaces, some packages use the UNIVERSAL module
as a holding area for some global subroutines that they
wish to export to everyone. I recommend that you do not
use this "feature" yourself (or at least not in those that
you contribute to CPAN!).
[reply]
RE: testFunction
by Anonymous Monk on Mar 24, 2000 at 08:57 UTC
    #
    sub method { }

package Pkg;
sub method_pkg { }

package main;
print defined '&method', "\n",
 main->can('method'), "\n",
 Pkg->can('method'), "\n",
 Pkg->can('method_pkg'), "\n";

#
[reply]

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