array_unique_validator.rb

require 'dry-validation'

class BulkPeriodValidator(array_of_periods)
  @array_of_periods = array_of_periods
  @schema = Dry::Validation.Schema do
    key(:array).required(:array?, :unique_by_endless_and_trial?)

    configure do
      # http://dry-rb.org/gems/dry-validation/error-messages/
      def self.messages
        Dry::Validation::Messages.default.merge(
          en: { errors: { unique_by_endless_and_trial?: 'must be unique values' } }
        )
      end

      # http://dry-rb.org/gems/dry-validation/custom-predicates/
      def unique_by_endless_and_trial?(value)
        values = value.select { |elem| [elem.endless, elem.trial] }
        values.size == values.uniq.size
      end
    end
  end

  def valid?
    !schema.(array: @array_of_periods).messages.any?
  end

  def errors
    schema.(array: @array_of_periods).messages
  end
end

period_validator = BulkPeriodValidator.new(array: your_array_of_periods)
period_validator.valid?
period_validator.errors