NAME
Evo::Class
VERSION
version 0.0217
DESCRIPTION
Mixins programming
A new promising inject-code programming concepts based on mixins. Documentation will be available if someone will be willing to help write it.
Why not OO and Moose like?
The most problems with Moose like modules is with initialization. Let's take a look:
package My::Moose;
use Moose;
has foo => is =>'rw';
package main;
my $obj = My::Moose->new(fo => 3);
print $obj->foo;As you can see, we passed fo instead of foo, and Moose silently ignored it. You should write a huge amout of extra tests to pervent such errors.
Also traditional OO programming suffers the fragile base class problems (use Google). To solve it, injection based Evo::Class introduces flexible roles Evo::Role.
SYNOPSYS
package main;
use Evo;
{
package My::Human;
use Evo -Class, -Loaded;
has 'name' => 'unnamed';
has 'gender', is => 'ro', required => 1;
has age => check => sub($v) { $v >= 18 };
sub greet($self) : Public { say "I'm " . $self->name }
}
my $alex = My::Human->new(gender => 'male');
# default value "unnamed"
say $alex->name;
# fluent design
$alex->name('Alex')->age(18);
say $alex->name, ': ', $alex->age;
# method
$alex->greet;
## ------------ protecting you from errors, uncomment to test
## will die, gender is required
#My::Human->new();
## will die, age must be >= 18
#My::Human->new(age => 17, gender => 'male');
#My::Human->new()->age(17, gender => 'male');
# --------- code reuse
{
package My::Developer;
use Evo -Class;
with 'My::Human'; # extends 'My::Human'; implements 'My::Human';
has lang => 'Perl';
sub show($self) : Public {
$self->greet();
say "I like ", $self->lang;
}
}
my $dev = My::Developer->new(gender => 'male');
$dev->show;Usage
creating an object
package My::Class;
use Evo -Class;
has 'simple';You don't need to call something like __PACKAGE__->meta->make_immutable unlike in Moose, Evo objects are fast enough by design.
new
my $foo = My::Class->new(simple => 1);
my $foo2 = My::Class->new();We're protected from common mistakes, because constructor won't accept unknown attributes
my $foo = My::Class->new(SiMple => 1);Storage
The big advantage of Evo object that it's not tied with implementation. The default uses hashes Evo::Class::Hash, but you can easily switch for example to Evo::Class::Out and use any other refs
Declaring attribute
package My::Foo;
use Evo '-Class *';
has 'simple';
has 'short' => 'value';
has 'foo' => default => 'value', is => 'rw', check => sub {1};Syntax
Simple rw attribute
has 'simple';
# has 'simple', is => 'rw';Attribute with default value: short form
has 'short' => 'value';
# has 'short', default => 'value';Full form
has 'foo' => default => 'value', is => 'rw', check => sub {1};Options
is
Can be 'rw' or 'ro'; Unlike Perl6 is 'rw' by default
default
Attribute will be filled with this value if isn't provided to the new constructor You can't use references, but you can provide a coderef instead of value, in this case return value of an invocation of this function will be used.
has ref => sub(%build_args) { {} };
has foo => default => sub(%build_args) { [] };This is a good way to init some attribute that should always exists. Arguments, passed to new or init will be passed to the function without object itself (because there are no object yet). If you're expecting another behaviour, check "lazy"
lazy
Like default, but will be filled at the first invocation, not in constructor, and an instance will be passed as the argument
# pay attention, an instance is passed
has foo => lazy => sub($self) { [] };required
Attributes with this options are required
check
You can provide function that will check passed value (via constuctor and changing), and if that function doesn't return true, an exception will be thrown.
has big => check => sub { shift > 10 };You can also return (0, "CustomError") to provide more expressive explanation
package main;
use Evo;
{
package My::Foo;
use Evo '-Class *';
has big => check => sub($val) { $val > 10 ? 1 : (0, "not > 10"); };
};
my $foo = My::Foo->new(big => 11);
$foo->big(9); # will die
my $bar = My::Foo->new(big => 9); # will dieCODE REUSE
Method should be marked with :Public if you want to reuse them; Attributes are all public;
Overriding
Evo protects you from method clashing. But if you want to override method or fix clashing, use "has_overriden" function or :Override attribute
package My::Peter;
use Evo -Class;
with 'My::Human';
has_overriden name => 'peter';
sub greet : Overriden { }This differs from traditional OO style. With compoment programming, you should reuse code via Evo::Class::Role or just organize classes with independed pieces of code like "mixing". So, try to override less
extends
Extends classes or roles
implements
Check if all required methods are implemented. Like interfaces
with
This does "extend + check implementation". Consider this example:
package main;
use Evo;
{
package My::Role::Happy;
use Evo -Class, -Loaded;
requires 'name';
sub greet($self) : Public {
say "My name is ", $self->name, " and I'm happy!";
}
package My::Class;
use Evo -Class;
has name => 'alex';
#extends 'My::Role::Happy';
#implements 'My::Role::Happy';
with 'My::Role::Happy';
}
My::Class->new()->greet();My::Role::Happy requires name in derivered class. We could install shared code with extends and then check implemantation with implements. Or just use with wich does both.
You may want to use extends and implements separately to resolve circular requirements, for example
CODE ATTRIBUTES
sub foo : Override { 'OVERRIDEN'; }Mark name as overriden. See "Overriding methods" in Evo::Role
AUTHOR
alexbyk.com
COPYRIGHT AND LICENSE
This software is copyright (c) 2016 by alexbyk.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.