Vladimir Nikonorov

There can be situations when we need dynamic validation of incoming params.

For example, we have a form with many fields that are stored in our database. Form fields can be added, deleted and customized by users. We would like to validate this form using convenient dry-validation gem syntax. Unfortunately, in dry-validation there is no way to do this:

class FormContract < Dry::Validation::Contract

  option :form_fields



  params do

    form_fields.each do |form_field|   # form_fields variable is not available in params block

      required(form_field.name).filled(:string)

    end

  end

end

We can validate our form in the following way:

class FormContractBuilder

  def self.schema(form_fields)

    form_contract = Class.new(Dry::Validation::Contract) {

      params do

        form_fields.each do |form_field|

          required(form_field.name).filled(:string)

        end

      end

    }



    form_contract.new

  end

end



FormContractBuilder.schema(form.fields).call(params)