dry-validation.rb

class UserValidator
  include Dry::Validation

  rules << {
    title: {
      inclusion: %w(Mr Mrs Miss Ms Dr)
    },
    first_name: {
      presence: true
    },
    last_name: {
      presence: true
    },
    username: {
      email: true
    }
  }
end

class RegistrationValidator < UserValidator
  rules << {
    username: {
      rescues: {
        exception: PG::UniqueViolation,
        as: :unique
      }
    },
    password: {
      length: 8..40
    }
  }
end

RegistrationValidator.new(params).transaction do

rescue Dry::Validation::Error => e

end