Nummy

Tasty enumeration utilities for Ruby

Nummy provides utilities that that build on Ruby's Enumerable module to provide functionality like enumerated types ("enums"), enumerating over constants in a module, and iterating over the members of data classes.

Note

This module does NOT add additional methods to the Enumerable module, or change its behavior in any way.

Installation

Install the gem and add to the application's Gemfile by executing:

bundle add nummy

If bundler is not being used to manage dependencies, install the gem by executing:

gem install nummy

Usage

To load nummy, use:

require "nummy"

This will lazily require (using autoload) the individual utilities as needed.

You can also explicitly load individual modules:

require "nummy/enum"
require "nummy/member_enumerable"
# ...

Nummy::Enum

The main feature of Nummy is the Nummy::Enum class, which is an opinionated class that can be used to define enumerated types ("enums") that use Ruby constants for the key-value pairs.

The recommended way to use Nummy::Enum is to define constants explicitly:

Creating (Recommended)

require "nummy"

class CardinalDirection < Nummy::Enum
  NORTH = 0
  EAST = 90
  SOUTH = 180
  WEST = 270
end

Tip

Statically defining the constants like this allows the enums to work really nicely out of the box with language servers like Ruby LSP because the fields are just statically defined constants. The sugary ways of defining enums (see below) use const_set behind the scenes, which does not work as well with language servers and tooling.

If you don't particularly care about the values, you can use the auto helper to define them automatically:

class Status < Nummy::Enum
  DRAFT = auto
  PUBLISHED = auto
  ARCHIVED = auto
end

Tip

auto comes from the Nummy::AutoSequenceable module, and has some extra features not shown in this example. For more information, see the section below on Nummy::AutoSequenceable.

Creating (Sugar)

There are also two sugary ways to define enums:

require "nummy"

Nummy.enum(NORTH: 0, EAST: 90, SOUTH: 180, WEST: 270)

# which is an alias for:
Nummy::Enum.define(NORTH: 0, EAST: 90, SOUTH: 180, WEST: 270)

Or if you want the values to be automatically generated:

require "nummy"
Status = Nummy.enum(:DRAFT, :PUBLISHED, :ARCHIVED)

Status.pairs
# => [[:DRAFT, 0], [:PUBLISHED, 1], [:ARCHIVED, 2]]

You can customize the generated enum by providing a block:

require "nummy"

Status = Nummy.enum(:DRAFT, :PUBLISHED, :ARCHIVED) do |enum|
  def self.custom_method
    puts "Hello from #{self}!"
  end
end

Status.custom_method
# => Hello from Status!

Working with enums

The Nummy::Enum class provides a number of methods for working with enums. For example, using the CardinalDirection example from above:

CardinalDirection.keys
# => [:NORTH, :EAST, :SOUTH, :WEST]

CardinalDirection.values
# => [0, 90, 180, 270]

CardinalDirection.pairs
# => [[:NORTH, 0], [:EAST, 90], [:SOUTH, 180], [:WEST, 270]]

CardinalDirection.include?(90)
# => true

They can even be used in case expressions to see if the case value is == to any of the values in the enum:

case some_angle
when CardinalDirection
  puts "The angle is a cardinal direction!"
else
  puts "Not a cardinal direction!"
end

Tip

Nummy::Enum extends Enumerable and iterates over the values of the enum, so you have access to things like .include?(value), .any?, and .find.

Rails / ActiveRecord integration

To use nummy enums as ActiveRecord enums, you can use the .to_attribute method, which converts the keys to snake_case by default:

class Conversation < ActiveRecord::Base
  class Status < Nummy::Enum
    ACTIVE = auto
    ARCHIVED = auto
  end

  enum :status, Status.to_attribute
end

Note

to_attribute will transform keys using String#underscore if it is defined, otherwise it will use Symbol#downcase.

Tip

You can also do custom transformations by passing a block to to_attribute. See the documentation for more details.

Using to_attribute allows you to use all of the Rails magic for enums, like scopes and boolean helpers, while also being able to refer to values in a safer way than hash lookups.

That is, these two are the same:

Conversation.statuses[:active] # => 0
Conversation::Status::ACTIVE   # => 0

But these are not:

Conversation.statuses[:acitve]
# => nil

Conversation::Status::ACITVE   # => nil
# =>
#  uninitialized constant Conversation::Status::ACITVE (NameError)
#  Did you mean?  Conversation::Status::ACTIVE

You can get similar behavior using #fetch:

Conversation.statuses.fetch(:acitve)
# => key not found: :acitve (KeyError)
#    Did you mean?  :active

But that still misses out on some of the DX benefits of using constants, like improved support for things like autocompletion, documentation, and navigation ("Go To Definition") in editors.

Nummy::MemberEnumerable

Nummy::MemberEnumerable is a module that includes Enumerable and makes it possible to iterate over any class or module that responds to members.

The motivation for this module is being able to iterate over Data classes that represent a finite collection of similar values.

require "nummy"

SomeCollection = Data.define(:foo, :bar, :baz) do
  include Nummy::MemberEnumerable
end

collection = SomeCollection[123, 456, 789]

collection.values
# => [123, 456, 789]

Note

The Nummy::MemberEnumerable module provides fewer enumeration features than you might expect, because it's modeled after Struct rather than Hash.

Nummy::ConstEnumerable

Nummy::ConstEnumerable is a module that only provides methods to iterate over the names, values, and pairs of a module's own constants. It is meant to provide low-level functionality for other classes, such as Nummy::Enum.

require "nummy"

module SomeModule
  extend Nummy::ConstEnumerable

  FOO = 123
  BAR = 456
  BAZ = 789
end

SomeModule.each_const_name { |name| puts name }
# => :BAR
# => :BAZ
# => :FOO

SomeModule.each_const_pair.to_a
# => [[:BAR, 456], [:BAZ, 789], [:FOO, 123]]

Warning

The enumeration order for Nummy::ConstEnumerable is not guaranteed because it uses Module#constants behind the scenes. If you require stable ordering, see Nummy::OrderedConstEnumerable.

Nummy::OrderedConstEnumerable

Nummy::OrderedConstEnumerable provides the same API as Nummy::ConstEnumerable, but guarantees three things:

• any constants defined before the module is extended will be sorted alphabetically before any other constants
• any constants defined after the module is extended will be sorted in insertion order
• the order of constants is stable across calls

For example:

require "nummy"

class CustomEnum
  BEFORE_C = :c
  BEFORE_B = :b
  BEFORE_A = :a

  extend Nummy::OrderedConstEnumerable

  AFTER_Z = :z
  AFTER_Y = :y
  AFTER_X = :x
end

CustomEnum.each_const_name.to_a
# => [:BEFORE_A, :BEFORE_B, :BEFORE_C, :AFTER_Z, :AFTER_Y, :AFTER_X]

Nummy::AutoSequenceable

Nummy::AutoSequenceable is a module that provides a single method, auto, which returns a unique value for each call. It is meant to provide low-level functionality for other classes, such as Nummy::Enum.

require "nummy"

class Weekday
  extend Nummy::AutoSequenceable
  
  SUNDAY = auto
  MONDAY = auto
  TUESDAY = auto
  WEDNESDAY = auto
  THURSDAY = auto
  FRIDAY = auto
  SATURDAY = auto
end

Weekday::SUNDAY
# => 0

Weekday::SATURDAY
# => 6

Like with iota in Go, or Enum.auto in Python, you can also customize the sequence behavior:

require "nummy"
require "bigdecimal"

module MetricPrefix
  extend Nummy::AutoSequenceable

  DECI  = auto(1) { |n| BigDecimal(10) ** -n }
  CENTI = auto
  MILLI = auto
  MICRO = auto(6)
  NANO  = auto(9)
  
  DECA = auto(1) { |n| BigDecimal(10) ** n }
  HECA = auto
  KILO = auto
  MEGA = auto(6)
  GIGA = auto(9)
end

MetricPrefix::DECI  # => 0.1e0
MetricPrefix::CENTI # => 0.1e-1
MetricPrefix::MILLI # => 0.1e-2
MetricPrefix::MICRO # => 0.1e-5
MetricPrefix::NANO  # => 0.1e-8

MetricPrefix::DECA  # => 0.1e2
MetricPrefix::HECA  # => 0.1e3
MetricPrefix::KILO  # => 0.1e4
MetricPrefix::MEGA  # => 0.1e7
MetricPrefix::GIGA  # => 0.1e10

See the implementation, tests, and documentation for more details.

Development

Setup

After checking out the repo, run bin/setup to install dependencies.

To install this gem onto your local machine, run bundle exec rake install.

Console

You can run bundle exec rake console for an interactive prompt that will allow you to experiment with the gem.

The console has a pre-configured Nummy::Enum that you can use for testing:

irb(main):001> CardinalDirection
=> #<CardinalDirection NORTH=0 EAST=90 SOUTH=180 WEST=270>
irb(main):002> CardinalDirection.values
=> [0, 90, 180, 270]

Documentation

You can start a documentation server by running rake docs. This will start a server at http://localhost:8808 that will pick up changes to the documentation whenever you refresh the page.

Note

If you make major changes to the gem, sometimes the server can get in a weird state and display incorrect documentation, especially on the sidebar. If this happens, you can try removing the yard cache with rm -rf .yardoc, then restart the server and refresh the docs page.

Testing

To run tests, you can use:

bundle exec rake test

Running subsets of tests

To run all of the tests in a specific file, you can use the TEST argument:

bundle exec rake test TEST="test/nummy/enum_test.rb"

To run a specific test by name, you can use the N argument and pass it a name or regex pattern:

bundle exec rake test N="/version/"

Tip

The N argument comes from Minitest::TestTask. See the Minitest README or the Minitest documentation for more information.

Tip

You can also combine multiple options together:

bundle exec rake test N="/positional args/" TEST=test/nummy/enum_test.rb

Coverage

Note

Coverage is not collected by default, because our configuration reports incorrect metrics when not run against the entire test suite. We could configure coverage to only report against files that were actually required, but because we lazily load some files, it would be easy to miss coverage for an entire file.

To collect coverage, you can set COVERAGE to true or 1:

bundle exec rake test COVERAGE=true

bundle exec rake test COVERAGE=1

Releasing

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 the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/bdchauvette/nummy. 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 No Attribution License.

Code of Conduct

Everyone interacting in the Nummy project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.