Now, what about data?
-=head2 A horse is a horse, of course of course -- or is it?
+=head2 A horse is a horse, of course of course, or is it?
Let's start with the code for the C<Animal> class
and the C<Horse> class:
list, as per usual.
Now for the fun part: Perl takes the class in which the instance was
-blessed, in this case C<Horse>, and uses that calss to locate the
+blessed, in this case C<Horse>, and uses that class to locate the
subroutine. In this case, C<Horse::sound> is found directly (without
using inheritance). In the end, it is as though our initial line were
written as follows:
Inside C<Horse::name>, the C<@_> array contains:
- (C<$horse>, "some", "unnecessary", "args")
+ ($horse, "some", "unnecessary", "args")
so the C<shift> stores C<$horse> into C<$self>. Then, C<$self> gets
de-referenced with C<$$self> as normal, yielding C<"Mr. Ed">.
Notice we're back to a class method, so the two arguments to
C<Horse::named> are C<Horse> and C<Mr. Ed>. The C<bless> operator
-not only blesses C<$name>, it also returns that reference.
+not only blesses C<\$name>, it also returns that reference.
This C<Horse::named> method is called a "constructor".
too. Therefore, it's never a good idea to define the data layout in a
way that's different from the data layout of the base classes. In fact,
it's a good idea to use blessed hash references in all cases. Also, this
-is also why it's important to have constructors do the low-level work.
-So, let's redefine C<Animal>:
+is why it's important to have constructors do the low-level work. So,
+let's redefine C<Animal>:
## in Animal
sub name {
=head2 Summary
-So, now we have class methods, constructors, instance methods,
-instance data, and even accessors. But that's still just the
-beginning of what Perl has to offer. We haven't even begun to talk
-about accessors that double as getters and setters, destructors,
-indirect object notation, subclasses that add instance data, per-class
-data, overloading, "isa" and "can" tests, C<UNIVERSAL> class, and so
-on. That's for the rest of the Perl documentation to cover.
-Hopefully, this gets you started, though.
+So, now we have class methods, constructors, instance methods, instance
+data, and even accessors. But that's still just the beginning of what
+Perl has to offer. We haven't even begun to talk about accessors that
+double as getters and setters, destructors, indirect object notation,
+overloading, "isa" and "can" tests, the C<UNIVERSAL> class, and so on.
+That's for the rest of the Perl documentation to cover. Hopefully, this
+gets you started, though.
=head1 SEE ALSO
=head1 COPYRIGHT
Copyright (c) 1999, 2000 by Randal L. Schwartz and Stonehenge
-Consulting Services, Inc. Permission is hereby granted to distribute
-this document intact with the Perl distribution, and in accordance
-with the licenses of the Perl distribution; derived documents must
-include this copyright notice intact.
+Consulting Services, Inc.
+
+Copyright (c) 2009 by Michael F. Witten.
+
+Permission is hereby granted to distribute this document intact with
+the Perl distribution, and in accordance with the licenses of the Perl
+distribution; derived documents must include this copyright notice
+intact.
Portions of this text have been derived from Perl Training materials
originally appearing in the I<Packages, References, Objects, and
projects / p5sagit/p5-mst-13.2.git / blobdiff