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/ Mojo::Base

NAME

Mojo::Base - Minimal base class for Mojo projects

SYNOPSIS


            

              
              
package Cat;
use Mojo::Base -base;
has name => 'Nyan';
has ['age', 'weight'] => 4;
package Tiger;
use Mojo::Base 'Cat';
has friend  => sub { Cat->new };
has stripes => 42;
package main;
use Mojo::Base -strict;
my $mew = Cat->new(name => 'Longcat');
say $mew->age;
say $mew->age(3)->weight(5)->age;
my $rawr = Tiger->new(stripes => 38, weight => 250);
say $rawr->tap(sub { $_->friend->name('Tacgnol') })->weight;

DESCRIPTION

Mojo::Base is a simple base class for Mojo projects with fluent interfaces.


            

              
              
# Automatically enables "strict", "warnings", "utf8" and Perl 5.16 features
use Mojo::Base -strict;
use Mojo::Base -base;
use Mojo::Base 'SomeBaseClass';
use Mojo::Base -role;

All four forms save a lot of typing. Note that role support depends on Role::Tiny (2.000001+).


            

              
              
# use Mojo::Base -strict;
use strict;
use warnings;
use utf8;
use feature ':5.16';
use mro;
# use Mojo::Base -base;
use strict;
use warnings;
use utf8;
use feature ':5.16';
use mro;
push @ISA, 'Mojo::Base';
sub has { Mojo::Base::attr(__PACKAGE__, @_) }
# use Mojo::Base 'SomeBaseClass';
use strict;
use warnings;
use utf8;
use feature ':5.16';
use mro;
require SomeBaseClass;
push @ISA, 'SomeBaseClass';
sub has { Mojo::Base::attr(__PACKAGE__, @_) }
# use Mojo::Base -role;
use strict;
use warnings;
use utf8;
use feature ':5.16';
use mro;
use Role::Tiny;
sub has { Mojo::Base::attr(__PACKAGE__, @_) }

On Perl 5.20+ you can also use the -signatures flag with all four forms and enable support for subroutine signatures.


            

              
              
# Also enable signatures
use Mojo::Base -strict, -signatures;
use Mojo::Base -base, -signatures;
use Mojo::Base 'SomeBaseClass', -signatures;
use Mojo::Base -role, -signatures;

If you have Future::AsyncAwait 0.52+ installed you can also use the -async_await flag to activate the async and await keywords to deal much more efficiently with promises. Note that this feature is EXPERIMENTAL and might change without warning!


            

              
              
# Also enable async/await
use Mojo::Base -strict, -async_await;
use Mojo::Base -base, -signatures, -async_await;

This will also disable experimental warnings on versions of Perl where this feature was still experimental.

FLUENT INTERFACES

Fluent interfaces are a way to design object-oriented APIs around method chaining to create domain-specific languages, with the goal of making the readability of the source code close to written prose.


            

              
              
package Duck;
use Mojo::Base -base, -signatures;
has 'name';
sub quack ($self) {
  my $name = $self->name;
  say "$name: Quack!"
}

Mojo::Base will help you with this by having all attribute accessors created with "has" (or "attr") return their invocant ($self) whenever they are used to assign a new attribute value.


            

              
              
Duck->new->name('Donald')->quack;

In this case the name attribute accessor is called on the object created by Duck->new. It assigns a new attribute value and then returns the Duck object, so the quack method can be called on it afterwards. These method chains can continue until one of the methods called does not return the Duck object.

FUNCTIONS

Mojo::Base implements the following functions, which can be imported with the -base flag or by setting a base class.

has


            

              
              
has 'name';
has ['name1', 'name2', 'name3'];
has name => 'foo';
has name => sub {...};
has ['name1', 'name2', 'name3'] => 'foo';
has ['name1', 'name2', 'name3'] => sub {...};
has name => sub {...}, weak => 1;
has name => undef, weak => 1;
has ['name1', 'name2', 'name3'] => sub {...}, weak => 1;

Create attributes for hash-based objects, just like the "attr" method.

METHODS

Mojo::Base implements the following methods.

attr


            

              
              
$object->attr('name');
SubClass->attr('name');
SubClass->attr(['name1', 'name2', 'name3']);
SubClass->attr(name => 'foo');
SubClass->attr(name => sub {...});
SubClass->attr(['name1', 'name2', 'name3'] => 'foo');
SubClass->attr(['name1', 'name2', 'name3'] => sub {...});
SubClass->attr(name => sub {...}, weak => 1);
SubClass->attr(name => undef, weak => 1);
SubClass->attr(['name1', 'name2', 'name3'] => sub {...}, weak => 1);

Create attribute accessors for hash-based objects, an array reference can be used to create more than one at a time. Pass an optional second argument to set a default value, it should be a constant or a callback. The callback will be executed at accessor read time if there's no set value, and gets passed the current instance of the object as first argument. Accessors can be chained, that means they return their invocant when they are called with an argument.

These options are currently available:

weak

            

              
              
weak => $bool

Weaken attribute reference to avoid circular references and memory leaks.

new


            

              
              
my $object = SubClass->new;
my $object = SubClass->new(name => 'value');
my $object = SubClass->new({name => 'value'});

This base class provides a basic constructor for hash-based objects. You can pass it either a hash or a hash reference with attribute values.

tap


            

              
              
$object = $object->tap(sub {...});
$object = $object->tap('some_method');
$object = $object->tap('some_method', @args);

Tap into a method chain to perform operations on an object within the chain (also known as a K combinator or Kestrel). The object will be the first argument passed to the callback, and is also available as $_. The callback's return value will be ignored; instead, the object (the callback's first argument) will be the return value. In this way, arbitrary code can be used within (i.e., spliced or tapped into) a chained set of object method calls.


            

              
              
# Longer version
$object = $object->tap(sub { $_->some_method(@args) });
# Inject side effects into a method chain
$object->foo('A')->tap(sub { say $_->foo })->foo('B');

with_roles


            

              
              
my $new_class = SubClass->with_roles('SubClass::Role::One');
my $new_class = SubClass->with_roles('+One', '+Two');
$object       = $object->with_roles('+One', '+Two');

Create a new class with one or more Role::Tiny roles. If called on a class returns the new class, or if called on an object reblesses the object into the new class. For roles following the naming scheme MyClass::Role::RoleName you can use the shorthand +RoleName. Note that role support depends on Role::Tiny (2.000001+).


            

              
              
# Create a new class with the role "SubClass::Role::Foo" and instantiate it
my $new_class = SubClass->with_roles('+Foo');
my $object    = $new_class->new;

SEE ALSO

Mojolicious, Mojolicious::Guides, https://mojolicious.org.