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YaEnum (Yet Another Enum)

NOTE: This gem is not stable yet. Use at your own risk.

Easily define enums in Ruby that aren't just symbols. Your enums can have associated values and methods. Imagine if Ruby had Rust's or Swift's enums.

Installation

Since this isn't published on rubygems.org yet, you'll have to

  1. Download the repo
  2. bundle install
  3. rake install

Usage

Basic API for defining enums:

module Colors
  extend YaEnum

  variant :Red do
    def rgb
      [255, 0, 0]
    end
  end

  variant :Blue do
    def rgb
      [0, 0, 255]
    end
  end
end

p Colors::Red.rgb # => [255, 0, 0]
p Colors::Blue.rgb # => [0, 0, 255]

You can also define methods outside the variants, which will be inherited by each variant

module Colors
  extend YaEnum

  variant :Red do
    def rgb
      [max, 0, 0]
    end
  end

  variant :Blue do
    def rgb
      [0, 0, max]
    end
  end

  def max
    255
  end
end

p Colors::Blue.rgb # => [0, 0, 255]
p Colors::Blue.max # 255

Enums can also have associated values:

module Colors
  extend YaEnum

  variant :Red, [:max] do
    def rgb
      [max, 0, 0]
    end
  end

  variant :Blue, [:max] do
    def rgb
      [0, 0, max]
    end
  end
end

p Colors::Red.new(max: 255).rgb # => [255, 0, 0]
p Colors::Blue.new(max: 255).rgb # => [0, 0, 255]

Enums can also be used in case statements:

module Colors
  extend YaEnum

  variant :Red, [:max]
  variant :Blue, [:max]
end

color = Colors::Red.new(max: 255)

case color
when Colors::Red
  puts "red!"
when Colors::Blue
  puts "blue!"
else
  raise "Unknown case"
end # => red!

If you forget to implement a method for a variant you'll get an exception:

module Colors
  extend YaEnum

  variant :Red, [:max] do
    def rgb
      [max, 0, 0]
    end
  end

  variant :Blue, [:max] do
  end
end

# Traceback (most recent call last):
#         5: from readme.rb:3:in `<main>'
#         4: from readme.rb:12:in `<module:Colors>'
#         3: from .../ya_enum/lib/ya_enum.rb:35:in `variant'
#         2: from .../ya_enum/lib/ya_enum.rb:49:in `ensure_all_methods_defined_for_each_variant!'
#         1: from .../ya_enum/lib/ya_enum.rb:49:in `each'
# .../ya_enum/lib/ya_enum.rb:54:in `block in ensure_all_methods_defined_for_each_variant!': Variant Blue is missing the following methods: (YaEnum::MissingMethods)
#   rgb

You can also use the .case method to ensure you're handling all cases

module Colors
  extend YaEnum

  variant :Red
  variant :Blue
end

color = Colors::Red

Colors.case(color) do |c|
  c.on(Colors::Red) do
    puts "red!"
  end

  c.on(Colors::Blue) do
    puts "blue!"
  end
end

This is different from a normal case statement because you'll get an YaEnum::Matcher::NonExhaustiveMatch exception if you forget to handle a case:

module Colors
  extend YaEnum

  variant :Red
  variant :Blue
end

color = Colors::Red

Colors.case(color) do |c|
  c.on(Colors::Red) do
    puts "red!"
  end
end

# Traceback (most recent call last):
#         5: from readme.rb:12:in `<main>'
#         4: from .../ya_enum/lib/ya_enum.rb:42:in `case'
#         3: from .../ya_enum/lib/ya_enum/matcher.rb:13:in `match_on'
#         2: from .../ya_enum/lib/ya_enum/matcher.rb:31:in `ensure_all_variants_handled!'
#         1: from .../ya_enum/lib/ya_enum/matcher.rb:31:in `each'
# .../ya_enum/lib/ya_enum/matcher.rb:33:in `block in ensure_all_variants_handled!': Variant Blue is not handled (YaEnum::Matcher::NonExhaustiveMatch)

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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/tonsser/ya_enum

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Enums for Ruby that aren't just symbols

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