operations.rb

    # dispatch method. can be put in base controller
    def op(klass)
      logger.info "Params: ", params.to_h
      obj = klass.new(params.to_h).register(:keystore, @keystore).register(:configstore, @configstore)
      resp = obj.process!(self, @context)
    rescue => e
      logger.error e.message
      raise e
    end

class Operation < Types::SafeStruct
  include Dry::Container::Mixin
  
  def process!(app) #app is a rack/controller object and is often used to call url_for
    begin
      res = validate
      raise Error400 unless res # the app server specific 400 exception class
    pre_process
    process(app) || {}
  end

  def process(app); end
  def pre_process; end
  def validate; true; end
end

class SampleOperation < Operation
  attribute :bank_id, Types::Optional::Int.default(0)
  attribute :telco_id, Types::Strict::Int.default(0)
  attribute :ambiguous, Types::Form::Bool.optional # accepts nil
  
  def validate
  end
  
  def process
  end
end