Contents

module Monolens
  module Object
    class Transform
      include Lens

      signature(Type::Object, Type::Object, {
        defn: [Type::Map.of(Type::Name, Type::Lenses), true],
        on_missing: [Type::Strategy.missing(%w{fail null skip}), false]
      })

      def initialize(options, registry)
        super(options, registry)
        ts = option(:defn, {})
        ts.each_pair do |k,v|
          ts[k] = lens(v)
        end
      end

      def call(arg, world = {})
        is_hash!(arg, world)

        result = arg.dup
        option(:defn, {}).each_pair do |attr, sub_lens|
          deeper(world, attr) do |w|
            actual_attr, fetched = fetch_on(attr, arg)
            if actual_attr
              result[actual_attr] = sub_lens.call(fetched, w)
            else
              on_missing(result, attr, world)
            end
          end
        end
        result
      end

      def on_missing(result, attr, world)
        strategy = option(:on_missing, :fail)
        case strategy&.to_sym
        when :fail
          fail!("Expected `#{attr}` to be defined", world)
        when :null
          result[attr] = nil
        when :skip
          nil
        else
          raise Monolens::Error, "Unexpected missing strategy `#{strategy}`"
        end
      end
      private :on_missing
    end
  end
end

Version data entries

5 entries across 5 versions & 1 rubygems

Version	Path
monolens-0.6.4	lib/monolens/stdlib/object/transform.rb
monolens-0.6.3	lib/monolens/stdlib/object/transform.rb
monolens-0.6.2	lib/monolens/stdlib/object/transform.rb
monolens-0.6.1	lib/monolens/stdlib/object/transform.rb
monolens-0.6.0	lib/monolens/stdlib/object/transform.rb