🪄 Magic Decorator
A bit of history: this gem was inspired by digging deeper into Draper with an eye on a refactoring.
It implements a general decorator logic. It’s not meant to be a presenter.
Installation
Install the gem and add to the application's Gemfile by executing:
$ bundle add magic-decorator
If bundler is not being used to manage dependencies, install the gem by executing:
$ gem install magic-decorator
Usage
Magic::Decorator::Base
is a basic decorator class to be inherited by any other decorator.
It further inherits from SimpleDelegator
and is straightforward like that.
class PersonDecorator < Magic::Decorator::Base
def name = "#{first_name} #{last_name}"
end
Person = Struct.new :first_name, :last_name do
include Magic::Decoratable
end
person = Person.new('John', 'Smith').decorate
person.name # => "John Smith"
Magic::Decoratable
This module adds three methods to decorate an object. Decorator class is being inferred automatically. When no decorator is found,
-
#decorate
returnsnil
, -
#decorate!
raisesMagic::Lookup::Error
, -
#decorated
returns the original object.
One can test for the object is actually decorated with #decorated?
.
'with no decorator for String'.decorated
.decorated? # => false
['with a decorator for Array'].decorated
.decorated? # => true
Extending decorator logic
When extending Magic::Decoratable
, one may override #decorator_base
to be used for lookup.
class Special::Decorator < Magic::Decorator::Base
def self.name_for object_class
"Special::#{object_class}Decorator"
end
end
module Special::Decoratable
include Magic::Decoratable
private
def decorator_base = Special::Decorator
end
class Special::Model
include Special::Decoratable
end
Special::Model.new.decorate # looks for Special::Decorator descendants
🪄 Magic
Decoratable scope
Magic::Decoratable
is mixed into Object
by default. It means that effectively any object is magically decoratable.
One can use Magic::Decoratable.classes
to see all the decoratable classes.
Decoration expansion
For almost any method called on a decorated object, both its result and yield
ed arguments get decorated.
'with no decorator for String'.decorated.chars
.decorated? # => false
['with a decorator for Array'].decorated.map(&:chars).first.grep(/\S/).group_by(&:upcase).transform_values(&:size).sort_by(&:last).reverse.first(5).map(&:first)
.decorated? # => true
Undecorated methods
Some methods aren’t meant to be decorated though:
-
deconstruct
&deconstruct_keys
for pattern matching, -
converting methods: those starting with
to_
, -
system methods: those starting with
_
.
undecorated
modifier
Magic::Decorator::Base.undecorated
can be used to exclude methods from being decorated automagically.
class MyDecorator < Magic::Decorator::Base
undecorated %i[to_s inspect]
undecorated :raw_method
undecorated :m1, :m2
end
Decorator class inference
Decorators provide automatic class inference for any object based on its class name powered by Magic Lookup.
For example, MyNamespace::MyModel.new.decorate
looks for MyNamespace::MyModelDecorator
first.
When missing, it further looks for decorators for its ancestor classes, up to ObjectDecorator
.
Default decorators
EnumerableDecorator
It automagically decorates all its decoratable items.
[1, [2], { 3 => 4 }, '5'].decorated
.map &:decorated? # => [false, true, true, false]
{ 1 => 2, [3] => [4] }.decorated.keys
.map &:decorated? # => [false, true]
{ 1 => 2, [3] => [4] }.decorated.values
.map &:decorated? # => [false, true]
{ 1 => 2, [3] => [4] }.decorated[1]
.decorated? # => false
{ 1 => 2, [3] => [4] }.decorated[[3]]
.decorated? # => true
Side effects for decorated collections
- enables splat operator:
*decorated
, - enables double-splat operator:
**decorated
, - enumerating methods yield decorated items.
Development
After checking out the repo, run bin/setup
to install dependencies. Then, run rake spec
to run the tests. You can also run bin/console
for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install
.
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/Alexander-Senko/magic-decorator. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.
License
The gem is available as open source under the terms of the MIT License.
Code of Conduct
Everyone interacting in the Magic Decorator project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.