EnumClass
This gem is an attempt to provide a lightweight solution for object-oriented enumerations in Ruby. It consists
in a single class (Enum
), that can be subclassed to create enumerations and comes with no dependencies. It's similar
in design to some other gems available, but
it stemmed out from the necessity of handling reliably missing features like inheritance and instance methods of the enumerated
object.
Installation
Add this line to your application's Gemfile:
gem 'enum_class'
And then execute:
$ bundle
Or install it yourself as:
$ gem install enum_class
Usage
Basic usage
class Foo < Enum
value :A
value :B
end
Foo.inspect # => Foo(A, B)
# Instances are accessible as constants
Foo::A.class # => Foo
Foo::B.class # => Foo
Foo::C # => raises NameError
# Enumerated values are implicitly ordered, depending on order of definition
Foo::A == Foo::B # => false
Foo::A < Foo::B # => true
# Instances can be retrieved by key
Foo[:a] # => Foo::A
Foo['a'] # => Foo::A
Foo.for('A') # => Foo::A
Foo.for('X') # => raises KeyError
Foo.new # => raises an error
# Helper methods
Foo.a # => Foo::A
Foo.b # => Foo::B
Foo::A.a? # => true
Foo::A.b? # => false
Creating enums with a shortcut
Bar = Enum.create(:a, :b, :c) # => Bar(A, B, C)
Custom initializer
class Foobar < Enum
def initialize(name)
@name = name
end
attr_reader :name
value :A, 'foo'
value :B, 'bar'
end
Foobar::A.name # => 'foo'
Foobar::B.name # => 'bar'
Inheritance
class Base < Enum
value :A
value :B
end
class Child < Base
value :C
end
Base.inspect # => Base(A, B)
Child.inspect # => Child(A, B, C)
:warning: If you reopen the base class later, the changes won't be reflected in the child. The values to inherit are evaluated at the time of the class definition.
Advanced inheritance with custom initializer
class Base < Enum
def initialize(name)
@name = name
end
attr_reader :name
value :A, 'foo'
value :B, 'bar'
end
class Child < Base
def initialize(name, number)
super(name)
@number = number
end
def initialize_from_superclass(superclass_enum_value)
super # default behavior is to copy all the instance variables
@number = superclass_enum_value.ord + 1
end
attr_reader :number
value :C, 'baz', 3
end
Child::C.name # => 'baz'
Child::C.number # => 3
Child::B.name # => 'bar'
Child::B.number # => 2
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
. To release a new version, update the version number in version.rb
, and then run bundle exec rake release
, which will create a git tag for the version, push git commits and tags, and push the .gem
file to rubygems.org.
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/LIQIDTechnology/enum_class. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.
License
The gem is available as open source under the terms of the MIT License.