=head1 DESCRIPTION
The Exporter module implements an C<import> method which allows a module
-to export functions and variables to its users' namespaces. Many modules
+to export functions and variables to its users' namespaces. Many modules
use Exporter rather than implementing their own C<import> method because
Exporter provides a highly flexible interface, with an implementation optimised
for the common case.
Perl automatically calls the C<import> method when processing a
-C<use> statement for a module. Modules and C<use> are documented
-in L<perlfunc> and L<perlmod>. Understanding the concept of
+C<use> statement for a module. Modules and C<use> are documented
+in L<perlfunc> and L<perlmod>. Understanding the concept of
modules and how the C<use> statement operates is important to
understanding the Exporter.
how to make inheritance work.)
As a general rule, if the module is trying to be object oriented
-then export nothing. If it's just a collection of functions then
-C<@EXPORT_OK> anything but use C<@EXPORT> with caution. For function and
+then export nothing. If it's just a collection of functions then
+C<@EXPORT_OK> anything but use C<@EXPORT> with caution. For function and
method names use barewords in preference to names prefixed with
ampersands for the export lists.
This imports only the symbols listed by the caller into their namespace.
All listed symbols must be in your C<@EXPORT> or C<@EXPORT_OK>, else an error
-occurs. The advanced export features of Exporter are accessed like this,
+occurs. The advanced export features of Exporter are accessed like this,
but with list entries that are syntactically distinct from symbol names.
=back
If any of the entries in an import list begins with !, : or / then
the list is treated as a series of specifications which either add to
-or delete from the list of names to import. They are processed left to
+or delete from the list of names to import. They are processed left to
right. Specifications are in the form:
[!]name This name only
A leading ! indicates that matching names should be deleted from the
list of names to import. If the first specification is a deletion it
-is treated as though preceded by :DEFAULT. If you just want to import
+is treated as though preceded by :DEFAULT. If you just want to import
extra names in addition to the default set you will still need to
include :DEFAULT explicitly.
=head2 Exporting without using Exporter's import method
Exporter has a special method, 'export_to_level' which is used in situations
-where you can't directly call Exporter's import method. The export_to_level
+where you can't directly call Exporter's
+import method. The export_to_level
method looks like:
MyPackage->export_to_level($where_to_export, $package, @what_to_export);
}
and you want to Export symbol C<$A::b> back to the module that called
-package A. Since Exporter relies on the import method to work, via
+package A. Since Exporter relies on the import method to work, via
inheritance, as it stands Exporter::import() will never get called.
Instead, say the following:
By including Exporter in your C<@ISA> you inherit an Exporter's import() method
but you also inherit several other helper methods which you probably don't
-want. To avoid this you can do
+want. To avoid this you can do
package YourModule;
use Exporter qw( import );
=head2 Module Version Checking
The Exporter module will convert an attempt to import a number from a
-module into a call to C<< $module_name->VERSION($value) >>. This can
+module into a call to C<< $module_name->VERSION($value) >>. This can
be used to validate that the version of the module being used is
greater than or equal to the required version.
Since the C<UNIVERSAL::VERSION> method treats the C<$VERSION> number as
a simple numeric value it will regard version 1.10 as lower than
-1.9. For this reason it is strongly recommended that you use numbers
+1.9. For this reason it is strongly recommended that you use numbers
with at least two decimal places, e.g., 1.09.
=head2 Managing Unknown Symbols
In some situations you may want to prevent certain symbols from being
-exported. Typically this applies to extensions which have functions
+exported. Typically this applies to extensions which have functions
or constants that may not exist on some systems.
The names of any symbols that cannot be exported should be listed
If a module attempts to import any of these symbols the Exporter
will give the module an opportunity to handle the situation before
-generating an error. The Exporter will call an export_fail method
+generating an error. The Exporter will call an export_fail method
with a list of the failed symbols:
@failed_symbols = $module_name->export_fail(@failed_symbols);
If the C<export_fail> method returns an empty list then no error is
-recorded and all the requested symbols are exported. If the returned
+recorded and all the requested symbols are exported. If the returned
list is not empty then an error is generated for each symbol and the
-export fails. The Exporter provides a default C<export_fail> method which
+export fails. The Exporter provides a default C<export_fail> method which
simply returns the list unchanged.
Uses for the C<export_fail> method include giving better error messages
Any names which are not tags are added to C<@EXPORT> or C<@EXPORT_OK>
unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
-names being silently added to C<@EXPORT> or C<@EXPORT_OK>. Future versions
+names being silently added to C<@EXPORT> or C<@EXPORT_OK>. Future versions
may make this a fatal error.
=head2 Generating combined tags
they can't be checked at compile time for constancy.
Even if a prototype is available at compile time, the body of the
-subroutine is not (it hasn't been C<AUTOLOAD>ed yet). perl needs to
+subroutine is not (it hasn't been C<AUTOLOAD>ed yet). perl needs to
examine both the C<()> prototype and the body of a subroutine at
compile time to detect that it can safely replace calls to that
subroutine with the constant value.
constructions are executed.
The ideal (but a bit ugly) way to never have to think
-about that is to use C<BEGIN> blocks. So the first part
+about that is to use C<BEGIN> blocks. So the first part
of the L</SYNOPSIS> code could be rewritten as:
package YourModule;
Any of these statements are nice replacements for
C<BEGIN { require Exporter; @ISA = qw(Exporter); }>
-with the same compile-time effect. The basic difference
+with the same compile-time effect. The basic difference
is that C<base> code interacts with declared C<fields>
while C<parent> is a streamlined version of the older
C<base> code to just establish the IS-A relationship.
For more details, see the documentation and code of
L<base> and L<parent>.
-Another thorough remedy to that runtime vs.
-compile-time trap is to use L<Exporter::Easy>,
+Another thorough remedy to that runtime
+vs. compile-time trap is to use L<Exporter::Easy>,
which is a wrapper of Exporter that allows all
boilerplate code at a single gulp in the
use statement.
=back
-There's one more item to add to this list. Do B<not>
-export variable names. Just because C<Exporter> lets you
+There's one more item to add to this list. Do B<not>
+export variable names. Just because C<Exporter> lets you
do that, it does not mean you should.
@EXPORT_OK = qw( $svar @avar %hvar ); # DON'T!
-Exporting variables is not a good idea. They can
+Exporting variables is not a good idea. They can
change under the hood, provoking horrible
effects at-a-distance, that are too hard to track
-and to fix. Trust me: they are not worth it.
+and to fix. Trust me: they are not worth it.
To provide the capability to set/get class-wide
settings, it is best instead to provide accessors
=head1 SEE ALSO
C<Exporter> is definitely not the only module with
-symbol exporter capabilities. At CPAN, you may find
-a bunch of them. Some are lighter. Some
-provide improved APIs and features. Peek the one
-that fits your needs. The following is
+symbol exporter capabilities. At CPAN, you may find
+a bunch of them. Some are lighter. Some
+provide improved APIs and features. Peek the one
+that fits your needs. The following is
a sample list of such modules.
Exporter::Easy
=head1 LICENSE
-This library is free software. You can redistribute it
+This library is free software. You can redistribute it
and/or modify it under the same terms as Perl itself.
=cut
projects / platform / upstream / perl.git / commitdiff