NAME
Object::Simple - Simple class builder(Mojo::Base porting)
SYNOPSIS
package SomeClass;
use Object::Simple -base;
# Create accessor
has 'foo';
# Create accessor with default value
has foo => 1;
has foo => sub { [] };
has foo => sub { {} };
has foo => sub { OtherClass->new };
# Create accessors at once
has [qw/foo bar baz/];
has [qw/foo bar baz/] => 0;
Create object.
# Create a new object
my $obj = SomeClass->new;
my $obj = SomeClass->new(foo => 1, bar => 2);
my $obj = SomeClass->new({foo => 1, bar => 2});
# Set and get value
my $foo = $obj->foo;
$obj->foo(1);
# set-accessor can be changed
$obj->foo(1)->bar(2);
Inheritance
# Foo.pm
package Foo;
use Object::Simple -base;
# Bar.pm
package Bar;
use Foo -base;
# Bar.pm (another way to inherit)
package Bar;
use Object::Simple -base => 'Foo';
DESCRIPTION
Object::Simple is Mojo::Base porting. you can use Mojo::Base features.
Object::Simple is a generator of accessor method, such as Class::Accessor, Mojo::Base, or Moose.
Class::Accessor is simple, but lack offten used features. new
method can't receive hash arguments. Default value can't be specified. If multipule values is set through the accessor, its value is converted to array reference without warnings.
Some people find Moose too complex, and dislike that it depends on outside modules. Some say that Moose is almost like another language and does not fit the familiar perl syntax. In some cases, in particular smaller projects, some people feel that Moose will increase complexity and therefore decrease programmer efficiency. In addition, Moose can be slow at compile-time and its memory usage can get large.
Object::Simple is the middle way between Class::Accessor and complex class builder. Only offten used features is implemented has no dependency. Object::Simple is almost same as Mojo::Base.
new
method can receive hash or hash reference. You can specify default value.
If you like Mojo::Base, Object::Simple is good choice.
GUIDE
1. Create accessor
At first, you create class.
package SomeClass;
use Object::Simple -base;
By using -base
option, SomeClass inherit Object::Simple and import has
method.
Object::Simple have new
method. new
method is constructor. new
method can receive hash or hash reference.
my $obj = SomeClass->new;
my $obj = SomeClass->new(foo => 1, bar => 2);
my $obj = SomeClass->new({foo => 1, bar => 2});
Create accessor by using has
function.
has 'foo';
If you create accessor, you can set or get attribute value.s
# Set value
$obj->foo(1);
# Get value
my $foo = $obj->foo;
set-accessor can be changed.
$obj->foo(1)->bar(2);
You can define default value.
has foo => 1;
If foo
attribute value is not exists, default value is used.
my $foo_default = $obj->foo;
If you want to use reference or object as default value, default value must be surrounded by code reference. the return value become default value.
has foo => sub { [] };
has foo => sub { {} };
has foo => sub { SomeClass->new };
You can create multiple accessors at once.
has [qw/foo bar baz/];
has [qw/foo bar baz/] => 0;
Class example
I introduce Object::Simple example.
Point class: two accessor x
and y
, and clear
method to set x
and y
to 0.
package Point;
use Object::Simple -base;
has x => 0;
has y => 0;
sub clear {
my $self = shift;
$self->x(0);
$self->y(0);
}
Use Point class.
use Point;
my $point = Point->new(x => 3, y => 5);
print $point->x;
$point->y(9);
$point->clear;
Point3D class: Point3D inherit Point class. Point3D class has z
accessor in addition to x
and y
. clear
method is overriden to clear x
, y
and z
.
package Point3D;
use Point -base;
has z => 0;
sub clear {
my $self = shift;
$self->SUPER::clear;
$self->z(0);
}
Use Point3D class.
use Point3D;
my $point = Point->new(x => 3, y => 5, z => 8);
print $point->z;
$point->z(9);
$point->clear;
2. Concepts of Object-Oriented programing
I introduce concepts of Object-Oriented programing
Inheritance
I explain the essence of Object-Oriented programing.
First concept is inheritance. Inheritance means that if Class Q inherit Class P, Class Q use all methods of class P.
+---+
| P | Base class
+---+ have method1 and method2
|
+---+
| Q | Sub class
+---+ have method3
Class Q inherits Class P, Q can use all methods of P in addition to methods of Q.
In other words, Q can use method1
, method2
, and method3
You can use -base
option to inherit class.
# P.pm
package P;
use Object::Simple -base;
sub method1 { ... }
sub method2 { ... }
# Q.pm
package Q;
use P -base;
sub method3 { ... }
Perl have useful functions and methods to help Object-Oriented programing.
If you know what class the object is belonged to, use ref
function.
my $class = ref $obj;
If you know what class the object inherits, use isa
method.
$obj->isa('SomeClass');
If you know what method the object(or class) can use, use can
method
SomeClass->can('method1');
$obj->can('method1');
Encapsulation
Second concept is encapsulation. Encapsulation means that you don't touch internal data directory. You must use public method when you access internal data.
Create accessor and use it to keep thie rule.
my $value = $obj->foo;
$obj->foo(1);
Polymorphism
Third concept is polymorphism. Polymorphism is divided into two concepts, overload and override
Perl programer don't need to care overload. Perl is dynamic type language. Subroutine can receive any value.
Override means that you can change method behavior in sub class.
# P.pm
package P;
use Object::Simple -base;
sub method1 { return 1 }
# Q.pm
package Q;
use P -base;
sub method1 { return 2 }
P method1
return 1. Q method1
return 2. Q method1
override P method1
.
# P method1 return 1
my $obj_a = P->new;
$obj_p->method1;
# Q method1 return 2
my $obj_b = Q->new;
$obj_q->method1;
If you want to use super class method from sub class, use SUPER pseudo-class.
package Q;
sub method1 {
my $self = shift;
# Call supper class P method1
my $value = $self->SUPER::method1;
return 2 + $value;
}
If you understand three concepts, you have learned Object-Oriented programming primary parts.
3. Often used techniques
Override new method
new
method can be overridden.
Example:
Initialize the object
sub new {
my $self = shift->SUPER::new(@_);
# Initialization
return $self;
}
Example:
Change arguments of new
.
sub new {
my $self = shift;
$self->SUPER::new(x => $_[0], y => $_[1]);
return $self;
}
You can pass array to new
method.
my $point = Point->new(4, 5);
IMPORT OPTIONS
-base
By using -base
option, the class inherit Object::Simple and import has
function.
package Foo;
use Object::Simple -base;
has x => 1;
has y => 2;
strict and warnings is automatically enabled.
You can also use -base
option in sub class to inherit other class.
# Bar inherit Foo
package Bar;
use Foo -base;
You can also use the following syntax.
# Same as above
package Bar;
use Object::Simple -base => 'Foo';
FUNCTIONS
has
Create accessor.
has 'foo';
has [qw/foo bar baz/];
has foo => 1;
has foo => sub { {} };
Create accessor. has
receive accessor name and default value. Default value is optional. If you want to create multipule accessors at once, specify accessor names as array reference at first argument.
If you want to specify reference or object as default value, it must be code reference not to share the value with other objects.
Get and set a attribute value.
my $foo = $obj->foo;
$obj->foo(1);
If a default value is specified and the value is not exists, you can get default value.
If a value is set, the accessor return self object. So you can set a value repeatedly.
$obj->foo(1)->bar(2);
You can create all accessors at once.
has [qw/foo bar baz/],
pot => 1,
mer => sub { 5 };
METHODS
new
my $obj = Object::Simple->new(foo => 1, bar => 2);
my $obj = Object::Simple->new({foo => 1, bar => 2});
Create a new object. new
receive hash or hash reference as arguments.
attr
__PACKAGE__->attr('foo');
__PACKAGE__->attr([qw/foo bar baz/]);
__PACKAGE__->attr(foo => 1);
__PACKAGE__->attr(foo => sub { {} });
__PACKAGE__->attr(
[qw/foo bar baz/],
pot => 1,
mer => sub { 5 }
);
Create accessor. attr
method usage is equal to has
method.
DEPRECATED FUNCTIONALITY
class_attr method # will be removed 2017/1/1
dual_attr method # will be removed 2017/1/1
BACKWARDS COMPATIBILITY POLICY
If a functionality is DEPRECATED, you can know it by DEPRECATED warnings. You can check all DEPRECATED functionalities by document. DEPRECATED functionality is removed after five years, but if at least one person use the functionality and tell me that thing I extend one year each time he tell me it.
EXPERIMENTAL functionality will be changed without warnings.
(This policy was changed at 2011/10/22)
BUGS
Tell me the bugs by mail or github http://github.com/yuki-kimoto/Object-Simple
AUTHOR
Yuki Kimoto, <kimoto.yuki at gmail.com>
COPYRIGHT & LICENSE
Copyright 2008-2016 Yuki Kimoto, all rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Artistic v2(This is same as Mojolicious licence).