example.rb

module BaseCommand
  module ClassMethods
    def schema(&block)
      @schema = Dry::Validation.Form(&block)
    end

    def build(data)
      result = schema.call(data)

      if result.success?
        new(result.output)
      else
        result.errors
      end
    end
  end

  def self.included(base)
    base.extend(ClassMethods)
  end

  attr_reader :data

  def initialize(data)
    @data = data
  end
end

class CreateNoteCommand
  include BaseCommand

  schema do
    key(:author_name).required
    key(:text).required
  end
end