Homer - Simple prototype-based object system
use Homer;
# create a prototype object
my $person = Homer->new(
first_name => 'Generic',
last_name => 'Person',
say_hi => sub {
my $self = shift;
print "Hi, my name is ", $self->first_name, ' ', $self->last_name, "\n";
}
);
# create a new object based on it
my $homer = $person->extend(
first_name => 'Homer',
last_name => 'Simpson'
);
$homer->say_hi; # prints 'Hi, my name is Homer Simpson'
# let's extend even more
my $bart = $homer->extend(
first_name => 'Bart',
father => sub { print "My father's name is ", $_[0]->prot->first_name, "\n" }
);
$bart->say_hi; # prints 'Hi, my name is Bart Simpson'
$bart->father; # prints "My father's name is Homer"
Homer
is a very simple prototype-based object system, similar to JavaScript.
In a prototype based object system there are no classes. Objects are either directly created
with some attributes and methods, or cloned from existing objects, in which case the object
being cloned becomes the prototype of the new object. The new object inherits all attributes
and methods from the prototype. Attributes and methods can be overridden, and new ones can be
added. The new object can be cloned as well, becoming the prototype of yet another new object,
thus creating a possibly endless chain of prototypes.
Prototype-based objects can be very powerful and useful in certain cases. They can provide a quick way of solving problems. Plus, sometimes you just really need an object, but don't need a class. I like to think of prototype-based OO versus class-based OO as being similar to schema-less database systems versus relational database systems.
Homer
is a quick and dirty implementation of such a system in Perl. As Perl is a class-based
language, this is merely a hack. When an object is created, Homer
creates a specific class just
for it behind the scenes. When an object is cloned, a new class is created for the clone, with the
parent object's class pushed to the new one's @ISA
variable, thus providing inheritance.
I can't say this implementation is particularly smart or efficient, but it gives me what I need
and is very lightweight (Homer
has no non-core dependencies). If you need a more robust
solution, Class::Prototyped might fit your need.
-
Prototypes are created by calling
new()
on theHomer
class with a hash, holding attributes and methods:my $prototype = Homer->new( attr1 => 'value1', attr2 => 'value2', meth1 => sub { print "meth1" } ); $prototype->attr1; # value1 $prototype->attr2; # value2 $prototype->meth1; # prints "meth1"
-
A list of all pure-attributes of an object (i.e. not methods) can be received by calling
attributes()
on the object.$prototype->attributes; # ('attr1', 'attr2')
-
Every object created by Homer can be cloned using
extend( %attrs )
. The hash can contain new attributes and methods, and can override existing ones.my $clone = $prototype->extend( attr2 => 'value3', meth2 => sub { print "meth2" } ); $clone->attr1; # value1 $clone->attr2; # value3 $clone->meth1; # prints "meth1" $clone->meth2; # prints "meth2"
-
Objects based on a prototype can refer to their prototype using the
prot()
method:$clone->prot->attr2; # value2
-
All attributes are read-write:
$clone->attr1('value4'); $clone->attr1; # value4 $clone->prot->attr1; # still value1
-
New methods can be added to an object after its construction. If the object is a prototype of other objects, they will immediately receive the new methods too.
$prototype->add_method('meth3' => sub { print "meth3" }); $clone->can('meth3'); # true
-
New attributes can't be added after construction (for now).
-
Cloned objects can be cloned too, creating a chain of prototypes:
my $clone2 = $clone->extend; my $clone3 = $clone2->extend; $clone3->prot->prot->prot; # the original $prototype
Creates a new prototype object with the provided attributes and methods (if any).
Homer
requires no configuration files or environment variables.
None other than Carp.
Please report any bugs or feature requests to
bug-Homer@rt.cpan.org
, or through the web interface at
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Homer.
You can find documentation for this module with the perldoc command.
perldoc Homer
You can also look for information at:
-
RT: CPAN's request tracker
-
AnnoCPAN: Annotated CPAN documentation
-
CPAN Ratings
-
Search CPAN
Ido Perlmuter ido@ido50.net
Copyright 2017 Ido Perlmuter
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.