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Author: comdog
Date: Wed Jun 11 15:12:22 2008
New Revision: 11409
Modified:
perlfaq/trunk/perlfaq7.pod
Log:
* How can I find out my current package?
+ replaced answer
+ reference perldata for __PACKAGE__
+ used blessed() instead of ref()
+ mention caller()
+ mention main and empty packages
Modified: perlfaq/trunk/perlfaq7.pod
==============================================================================
--- perlfaq/trunk/perlfaq7.pod (original)
+++ perlfaq/trunk/perlfaq7.pod Wed Jun 11 15:12:22 2008
@@ -819,20 +819,42 @@
=head2 How can I find out my current package?
-If you're just a random program, you can do this to find
-out what the currently compiled package is:
-
- my $packname = __PACKAGE__;
+(contributed by brian d foy)
-But, if you're a method and you want to print an error message
-that includes the kind of object you were called on (which is
-not necessarily the same as the one in which you were compiled):
-
- sub amethod {
- my $self = shift;
- my $class = ref($self) || $self;
- warn "called me from a $class object";
- }
+To find the package you are currently in, use the special literal
+C<__PACKAGE__>, as documented in L<perldata>. You can only use the
+special literals as separate tokens, so you can't interpolate them
+into strings like you can with variables:
+
+ my $current_package = __PACKAGE__;
+ print "I am in package $current_package\n";
+
+This is different from finding out the package an object is blessed
+into, which might not be the current package. For that, use C<blessed>
+from C<Scalar::Util>, part of the Standard Library since Perl 5.8:
+
+ use Scalar::Util qw(blessed);
+ my $object_package = blessed( $object );
+
+Most of the time, you shouldn't care what package an object is blessed
+into, however, as long as it claims to inherit from that class:
+
+ my $is_right_class = eval { $object->isa( $package ) }; # true or false
+
+If you want to find the package calling your code, perhaps to give better
+diagnostics as C<Carp> does, use the C<caller> built-in:
+
+ sub foo {
+ my @args = ...;
+ my( $package, $filename, $line ) = caller;
+
+ print "I was called from package $package\n";
+ );
+
+By default, your program starts in package C<main>, so you should
+always be in some package unless someone uses the C<package> built-in
+with no namespace. See the C<package> entry in L<perlfunc> for the
+details of empty packges.
=head2 How can I comment out a large block of perl code?
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