Data class factory

Backport Data.define for Ruby 2.7, 3.0, 3.1 :)

gem 'data_class_factory'

and then bundle install

require 'data_class_factory'

Point = Data.define(:x, :y) do
  def norm
    Math.sqrt(x * x + y * y)
  end
end
p1 = Point.new(x: 3, y: 4)
p2 = Point.new(x: 3, y: 4)
p1 == p2 # => true

Most features of the data class are ported. See https://docs.ruby-lang.org/en/3.2/Data.html for checking the original spec of Data.

One difference is that backported Data class intentionally accepts only keyword arguments for .new while original Data class accepts both positional args and keyword args.

Point = Data.define(:x, :y) do
  def norm
    Math.sqrt(x * x + y * y)
  end
end

# raises ArgumentError
#          wrong number of arguments (given 2, expected 0)
p1 = Point.new(3, 4)

p1 = Point.new(x: 3, y: 4) # works well :)

REMARK this gem removes Data defined on Ruby 2.7, and respects original Data on Ruby >= 3.2. If you prefer using this gem also on Ruby >= 3.2, choose another name like this.

MyDataClass = DataClassFactory.define_factory_class

We can use the aliased class as usual like below.

Point = MyDataClass.define(:x, :y) do
  def norm
    Math.sqrt(x * x + y * y)
  end
end

The gem is available as open source under the terms of the MIT License.

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