> -----Message d'origine-----
> De�: Charles K. Clarkson [mailto:[EMAIL PROTECTED]
> Envoy�: mercredi 16 mars 2005 19:27
> ��: [email protected]
> Objet�: RE: build perl modules
>
> What you are describing is called "exporting" (or "importing" --
> depending on how you look at it.). There is a module which probably
> came with your perl distribution. It is named Exporter.pm and it will
> ease building modules like the one you describe. Read its
> documentation for more details.
>
>
> Let's begin writing our new module with a subroutine we will
> probably rarely use, but hate to have to rewrite each time we need
> it. The truth is, it is not hard to write, just hard to remember.
>
> sub Identity {
> return @_;
> }
>
> Wow. That's a long one. We are now ready to create the module.
>
> package SpecialSubs;
>
> sub Identity {
> return @_;
> }
>
> 1;
>
> This module is all we really need. Create a file like this
> and name it "SpecialSubs.pm". Come back when your done. The "1;" at
> the end is very important. It is needed on all modules.
>
> =========
>
> Okay, you're back. Now let's create a script in our favorite
> editor and run it.
>
> #!/usr/bin/perl
>
> use strict;
> use warnings;
>
> use SpecialSubs;
>
> print SpecialSubs::Identity( 'foo' );
>
> __END__
>
>
> Prefixing every sub with "SpecialSubs::" could get old quick.
> When we "use" a module a series of events occur. One of those events
> is running a subroutine named "import" if it is present.
>
> Let's go back to the module and add an "import" sub
>
> package SpecialSubs;
>
> sub import {
> print "This is the import sub running automatically\n";;
> }
>
>
> sub Identity {
> return @_;
> }
>
> 1;
>
> We'll also change our script.
>
> #!/usr/bin/perl
>
> use strict;
> use warnings;
>
> use SpecialSubs;
>
> __END__
>
> Run this and you'll see that the import sub is called
> automatically. We can use the import sub to "import"
> subroutines into your script.
>
>
> The caller() function from perl will tell us the details
> about how this module was called.
>
> package SpecialSubs;
>
> sub import {
> my( $name_space, $script, $line_number ) = caller();
> printf qq(%s "use"d by %s on line %s in package "%s".\n),
> 'SpecialSubs::import()',
> $script,
> $line_number,
> $name_space;
> }
>
>
> sub Identity {
> return @_;
> }
>
> 1;
>
> Running our script now reveals which package has called
> SpecialSubs.pm. We can get just the name space of the caller
> with this.
>
> package SpecialSubs;
>
> sub import {
> my $name_space = caller();
> print $name_space;
> }
>
>
> sub Identity {
> return @_;
> }
>
> 1;
>
> Knowing the name space of the caller, we can import items
> into it's name space. We need to use symbolic references here.
> Usually, new perl programmers should avoid symbolic references.
>
> package SpecialSubs;
>
> sub import {
> my $caller = caller();
> *{$caller . '::Identity'} = \&Identity;
> }
>
>
> sub Identity {
> return @_;
> }
>
> 1;
>
> If there were 100 subs in the module this could get a
> little long and sometimes we need more control. For example,
> we might need just two subs and are now stuck with 98 subs we
> don't need. We also didn't do any error checking.
>
> Exporter.pm comes to the rescue. Using this module to
> build our modules makes life more simple.
>
>
> package SpecialSubs;
>
> require Exporter;
> @ISA = qw(Exporter);
>
> @EXPORT_OK = qw( Identity );
>
> sub Identity {
> return @_;
> }
>
> 1;
>
>
>
> #!/usr/bin/perl
>
> use strict;
> use warnings;
>
> use SpecialSubs qw( Identity );
>
> print Identity( 'foo' );
>
> __END__
>
>
> If you'd rather use strict and warnings in the module
> you'll need this.
>
> package SpecialSubs;
>
> use strict;
> use warnings;
>
> use vars qw( @ISA @EXPORT_OK );
>
> require Exporter;
> @ISA = qw(Exporter);
>
> @EXPORT_OK = qw( Identity );
>
> sub Identity {
> return @_;
> }
>
> 1;
>
>
> OR:
>
> package SpecialSubs;
>
> use strict;
> use warnings;
>
> our( qw( @ISA @EXPORT_OK ) );
>
> require Exporter;
> @ISA = qw(Exporter);
>
> @EXPORT_OK = qw( Identity );
>
> sub Identity {
> return @_;
> }
>
> 1;
>
>
> HTH,
>
> Charles K. Clarkson
> --
> Mobile Homes Specialist
> 254 968-8328
+1
Nicely explained ;)
Someone who want to avoid writing inheritance (@ISA) from Exporter,
can write something like:
package SpecialSubs;
use strict;
use warnings;
use UNIVERSAL::exports;
@EXPORT_OK = qw( Identity );
sub Identity {
return @_;
}
1;
for more info, see:
http://search.cpan.org/~mschwern/UNIVERSAL-exports-0.03
Jos�.
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