Ruby Monads

input.rb

require "dry/monads"
include Dry::Monads[:maybe]

class Presenter
  class << self
    def presents(name, &block)
      presentations[name] = block
    end

    def perform(**presentables)
      presentables.each_with_object({}) { |(name, value), presented|
        presented[name] = present(name, value)
      }
    end

    private def presentations
      @presentations ||= {}
    end

    private def present(name, value)
      if block = presentations[name]
        block.call(value)
      else
        nil
      end
    end
  end
end

class AddressPresenter < Presenter
  presents :address do |address|
    address || "no address"
  end
end

AddressPresenter.perform(address: "foo")
# => { address: "foo" }

AddressPresenter.perform(address: nil)
# => { address: "no address" }

AddressPresenter.perform(address: Maybe(nil).maybe(&:address))
# { address: None }

# Is the correct solution to unwrap the value before passing it along?
#
AddressPresenter.perform(address: Maybe(nil).maybe(&:address).value_or(nil))
# { address: "no address" }