Mic - Simplified OOP with emphasis on modularity and loose coupling.
# The evolution of a simple Set class: package Example::Synopsis::Set; use Mic::Class interface => { object => { add => {}, has => {}, }, class => { new => {}, } }, implementation => 'Example::Synopsis::ArraySet', ; 1; # And the implementation for this class: package Example::Synopsis::ArraySet; use Mic::Impl has => { SET => { default => sub { [] } } }, ; sub has { my ($self, $e) = @_; scalar grep { $_ == $e } @{ $self->[SET] }; } sub add { my ($self, $e) = @_; if ( ! $self->has($e) ) { push @{ $self->[SET] }, $e; } } 1; # Now we can use it use Test::More tests => 2; use Example::Synopsis::Set; my $set = Example::Synopsis::Set::->new; ok ! $set->has(1); $set->add(1); ok $set->has(1); # But this has O(n) lookup and we can do better, so: package Example::Synopsis::HashSet; use Mic::Impl has => { SET => { default => sub { {} } } }, ; sub has { my ($self, $e) = @_; exists $self->[SET]{$e}; } sub add { my ($self, $e) = @_; ++$self->[SET]{$e}; } 1; # Now to make use of this we can either: package Example::Synopsis::Set; use Mic::Class interface => { object => { add => {}, has => {}, }, class => { new => {}, } }, implementation => 'Example::Synopsis::HashSet'; # updated 1; # Or just use Test::More tests => 2; use Mic::Bind 'Example::Synopsis::Set' => 'Example::Synopsis::HashSet'; use Example::Synopsis::Set; my $set = Example::Synopsis::Set::->new; ok ! $set->has(1); $set->add(1); ok $set->has(1);
This is an early release available for testing and feedback and as such is subject to change.
Mic (Messages, Interfaces and Contracts) is a framework for simplifying the coding of OOP modules, with the following features:
Reduces the tedium and boilerplate code typically involved in creating object oriented modules.
Makes it easy to create classes that are modular and loosely coupled.
Enables trivial swapping of implementations (see Mic::Bind).
Encourages self documenting code.
Simplifies code verification via Eiffel style contracts.
Modularity means there is an obvious separation between what the users of an object need to know (the interface for using the object) and implementation details that users don't need to know about.
This separation of interface from implementation details is an important aspect of modular design, as it enables modules to be interchangeable (so long as they have the same interface).
It is not a coincidence that the Object Oriented concept as originally envisioned was mainly concerned with messaging, where in the words of Alan Kay (who coined the term "Object Oriented Programming") objects are "like biological cells and/or individual computers on a network, only able to communicate with messages" and "OOP to me means only messaging, local retention and protection and hiding of state-process, and extreme late-binding of all things." (see The Deep Insights of Alan Kay).
In the simplest scenario in which both interface and implementation are defined in the same file, a class can also be defined by calling the define_class() class method, with a hashref that specifies the class.
define_class()
The class defined in the SYNOPSIS could also be defined like this (in one file)
package Example::Usage::Set; use Mic; Mic->define_class({ interface => { object => { add => {}, has => {}, }, class => { new => {} } }, via => 'Example::Usage::HashSet', }); package Example::Usage::HashSet; use Mic::Impl has => { SET => { default => sub { {} } } }, ; sub has { my ($self, $e) = @_; exists $self->[SET]{$e}; } sub add { my ($self, $e) = @_; ++$self->[SET]{$e}; } 1;
For scenarios in which interfaces and implementations are defined in their own files, see Mic::Class and Mic::Interface.
The meaning of the keys in the specification hash are described next.
The interface is a group of messages that objects belonging to this class should respond to.
It can be specified as a reference to a hash, in which the values of the hash are contracts on the keys.
It can also be specified as a string that names a Mic::Interface package which defines the interface.
An exception is raised if this is empty or missing.
The messages named in this group must have corresponding subroutine definitions in a declared implementation, otherwise an exception is raised.
The interface consists of the following subsections:
Specifies the names of each method that these objects can respond to, as well as their contracts.
Specifies the names of each class method that the class can respond to, as well as their contracts.
See Mic::Contracts for more details about invariants.
Specifies the names of one or more super-interfaces. This means the interface will include any methods from the super-interfaces that aren't declared locally.
The name of a package that defines the subroutines declared in the interface.
Mic::Impl describes how implementations are configured.
An alias of "implementation" above.
If two or more classes share a common interface, we can reduce duplication by factoring out that interface using Mic::Interface, which expects an interface specified in the same way as interface
interface
Suppose we wanted to use both versions of the set class (from the synopsis) in the same program.
The first step is to extract the common interface:
package Example::Usage::SetInterface; use Mic::Interface object => { add => {}, has => {}, }, class => { new => {} } ; 1;
Then implementations of this interface can be loaded via load_class:
load_class
use Test::More tests => 4; use Example::Usage::SetInterface; my $HashSetClass = Mic->load_class({ interface => 'Example::Usage::SetInterface', implementation => 'Example::Synopsis::HashSet', }); Mic->load_class({ interface => 'Example::Usage::SetInterface', implementation => 'Example::Synopsis::ArraySet', name => 'ArraySet', }); my $a_set = 'ArraySet'->new; ok ! $a_set->has(1); $a_set->add(1); ok $a_set->has(1); my $h_set = $HashSetClass->new; ok ! $h_set->has(1); $h_set->add(1); ok $h_set->has(1);
load_class expects a hashref with the following keys:
The name of an interface declared via declare_interface.
declare_interface
The name of an implementation package.
The name of the class via which objects are created.
This is optional and if not given, a synthetic name is used. In either case this name is returned by load_class
Behavioural (method) and interface introspection are possible using $object->can and $object->DOES respectiively which if called with no argument will return a list (or array ref depending on context) of methods or interfaces supported by the object.
$object->can
$object->DOES
Also note that for any class Foo created using Mic, and for any object created with Foo's constructor, the following will always return a true value
Foo
$object->DOES('Foo')
Please report any bugs or feature requests via the GitHub web interface at https://github.com/arunbear/Mic/issues.
Stevan Little (for creating Moose), Tye McQueen (for numerous insights on class building and modular programming).
Arun Prasaad <arunbear@cpan.org>
Copyright 2014- Arun Prasaad
This library is free software; you can redistribute it and/or modify it under the terms of the GNU public license, version 3.
To install Mic, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Mic
CPAN shell
perl -MCPAN -e shell install Mic
For more information on module installation, please visit the detailed CPAN module installation guide.