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Man Pages
Object::Simple(3) User Contributed Perl Documentation Object::Simple(3)
 

Object::Simple - Simple class builder(Mojo::Base porting)

  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';

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.

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;

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;

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.

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);

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';

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/];

  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.

  __PACKAGE__->attr('foo');
  __PACKAGE__->attr([qw/foo bar baz/]);
  __PACKAGE__->attr(foo => 1);
  __PACKAGE__->attr(foo => sub { {} });
  __PACKAGE__->attr([qw/foo bar baz/]);
Create accessor. "attr" method usage is equal to "has" method.

  function exporting of C<new> and C<attr> method # Will be removed 2021/6/1
  
  The syntax of multiple key-value arguments 
    has x => 1, y => 2;      
    __PACAKGE__->attr(x => 1, y => 2);
  # Will be removed 2021/6/1
  
  class_attr method # will be removed 2017/1/1
  dual_attr method # will be removed 2017/1/1

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)

Tell me the bugs by mail or github <http://github.com/yuki-kimoto/Object-Simple>

Yuki Kimoto, "<kimoto.yuki at gmail.com>"

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).
2016-05-14 perl v5.28.1

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