the file Person.pm. If it were called a Happy::Person class, it would
be stored in the file Happy/Person.pm, and its package would become
Happy::Person instead of just Person. (On a personal computer not
-running Unix or Plan 9, but something like MacOS or VMS, the directory
+running Unix or Plan 9, but something like Mac OS or VMS, the directory
separator may be different, but the principle is the same.) Do not assume
any formal relationship between modules based on their directory names.
This is merely a grouping convenience, and has no effect on inheritance,
PEERS => [ "Norbert", "Rhys", "Phineas"],
};
-And so you could get at C<$rec-E<gt>{NAME}> to find "Jason", or
-C<@{ $rec-E<gt>{PEERS} }> to get at "Norbert", "Rhys", and "Phineas".
+And so you could get at C<< $rec->{NAME} >> to find "Jason", or
+C<< @{ $rec->{PEERS} } >> to get at "Norbert", "Rhys", and "Phineas".
(Have you ever noticed how many 23-year-old programmers seem to
be named "Jason" these days? :-)
Perl doesn't impose restrictions on who gets to use which methods.
The public-versus-private distinction is by convention, not syntax.
(Well, unless you use the Alias module described below in
-L</"Data Members as Variables">.) Occasionally you'll see method names beginning or ending
+L<Data Members as Variables>.) Occasionally you'll see method names beginning or ending
with an underscore or two. This marking is a convention indicating
that the methods are private to that class alone and sometimes to its
closest acquaintances, its immediate subclasses. But this distinction
sub exclaim {
my $self = shift;
return sprintf "Hi, I'm %s, age %d, working with %s",
- $self->{NAME}, $self->{AGE}, join(", ", $self->{PEERS});
+ $self->{NAME}, $self->{AGE}, join(", ", @{$self->{PEERS}});
}
Or maybe even one like this:
Notice how there's no memory to deallocate in the destructor? That's
something that Perl takes care of for you all by itself.
+Alternatively, you could use the Class::Data::Inheritable module from
+CPAN.
+
+
=head2 Accessing Class Data
It turns out that this is not really a good way to go about handling
}
What happens if a derived class (which we'll call Employee) inherits
-methods from this Person base class? Then C<Employee-E<gt>debug()>, when called
+methods from this Person base class? Then C<< Employee->debug() >>, when called
as a class method, manipulates $Person::Debugging not $Employee::Debugging.
=head2 Class Destructors
a method? Well, in principle, yes. A method is just a function that
expects as its first argument a class name (package) or object
(blessed reference). Person::new() is the function that both the
-C<Person-E<gt>new()> method and the C<Employee-E<gt>new()> method end
+C<< Person->new() >> method and the C<< Employee->new() >> method end
up calling. Understand that while a method call looks a lot like a
function call, they aren't really quite the same, and if you treat them
as the same, you'll very soon be left with nothing but broken programs.
If you wanted to add version checking to your Person class explained
above, just add this to Person.pm:
- use vars qw($VERSION);
- $VERSION = '1.1';
+ our $VERSION = '1.1';
and then in Employee.pm could you can say
package Person;
use Carp;
- use vars qw($AUTOLOAD); # it's a package global
+ our $AUTOLOAD; # it's a package global
my %fields = (
name => undef,
package Employee;
use Person;
use strict;
- use vars qw(@ISA);
- @ISA = qw(Person);
+ our @ISA = qw(Person);
my %fields = (
id => undef,
BEGIN {
use Exporter ();
- use vars qw(@EXPORT @EXPORT_OK %EXPORT_TAGS);
- @EXPORT = qw(gethostbyname gethostbyaddr gethost);
- @EXPORT_OK = qw(
- $h_name @h_aliases
- $h_addrtype $h_length
- @h_addr_list $h_addr
- );
- %EXPORT_TAGS = ( FIELDS => [ @EXPORT_OK, @EXPORT ] );
+ our @EXPORT = qw(gethostbyname gethostbyaddr gethost);
+ our @EXPORT_OK = qw(
+ $h_name @h_aliases
+ $h_addrtype $h_length
+ @h_addr_list $h_addr
+ );
+ our %EXPORT_TAGS = ( FIELDS => [ @EXPORT_OK, @EXPORT ] );
}
- use vars @EXPORT_OK;
+ our @EXPORT_OK;
# Class::Struct forbids use of @ISA
sub import { goto &Exporter::import }
}
use Alias qw(attr);
- use vars qw($NAME $AGE $PEERS);
+ our ($NAME, $AGE, $PEERS);
sub name {
my $self = attr shift;
return ++$AGE;
}
-The need for the C<use vars> declaration is because what Alias does
+The need for the C<our> declaration is because what Alias does
is play with package globals with the same name as the fields. To use
globals while C<use strict> is in effect, you have to predeclare them.
These package variables are localized to the block enclosing the attr()
It would be nice to combine Alias with
something like Class::Struct or Class::MethodMaker.
-=head2 NOTES
+=head1 NOTES
=head2 Object Terminology
call a class method (one expecting a string argument) on an
object (one expecting a reference), or vice versa.
-Z<>From the C++ perspective, all methods in Perl are virtual.
+From the C++ perspective, all methods in Perl are virtual.
This, by the way, is why they are never checked for function
prototypes in the argument list as regular builtin and user-defined
functions can be.
and
L<overload>.
-=head1 COPYRIGHT
+L<perlboot> is a kinder, gentler introduction to object-oriented
+programming.
+
+L<perltooc> provides more detail on class data.
+
+Some modules which might prove interesting are Class::Accessor,
+Class::Class, Class::Contract, Class::Data::Inheritable,
+Class::MethodMaker and Tie::SecureHash
+
-I I<really> hate to have to say this, but recent unpleasant
-experiences have mandated its inclusion:
-
- Copyright 1996 Tom Christiansen. All Rights Reserved.
-
-This work derives in part from the second edition of I<Programming Perl>.
-Although destined for release as a manpage with the standard Perl
-distribution, it is not public domain (nor is any of Perl and its docset:
-publishers beware). It's expected to someday make its way into a revision
-of the Camel Book. While it is copyright by me with all rights reserved,
-permission is granted to freely distribute verbatim copies of this
-document provided that no modifications outside of formatting be made,
-and that this notice remain intact. You are permitted and encouraged to
-use its code and derivatives thereof in your own source code for fun or
-for profit as you see fit. But so help me, if in six months I find some
-book out there with a hacked-up version of this material in it claiming to
-be written by someone else, I'll tell all the world that you're a jerk.
-Furthermore, your lawyer will meet my lawyer (or O'Reilly's) over lunch
-to arrange for you to receive your just deserts. Count on it.
+=head1 AUTHOR AND COPYRIGHT
+
+Copyright (c) 1997, 1998 Tom Christiansen
+All rights reserved.
+
+This documentation is free; you can redistribute it and/or modify it
+under the same terms as Perl itself.
+
+Irrespective of its distribution, all code examples in this file
+are hereby placed into the public domain. You are permitted and
+encouraged to use this code in your own programs for fun
+or for profit as you see fit. A simple comment in the code giving
+credit would be courteous but is not required.
+
+=head1 COPYRIGHT
=head2 Acknowledgments
https://perl5.git.perl.org / perl5.git / blobdiff