A JSON object that encodes its pairs in the order given.

Elixir maps do not preserve insertion order at any size. The API treats a Choice question's criteria as an ordered list of options (the order is what the model sees), so Choice criteria travel as this struct rather than as a map.

JSON.encode!(%TypeSafeAPI.JSON.OrderedObject{pairs: [{"b", 1}, {"a", nil}]})
#=> ~s({"b":1,"a":null})

Keys must be atoms or strings, and new/1 says so at construction rather than letting a bad key surface from inside the encoder at request time. Values may be anything JSON can encode.

It is not a map

This is a struct, so is_map/1 returns true for it and map_size/1 returns its field count, not its pair count. Anything that inspects a wire object generically should use Enum instead: the struct implements Enumerable over its {key, value} pairs, so Enum.count/1, Enum.map/2 and Enum.into/2 all work and see the pairs in order.

object = TypeSafeAPI.JSON.OrderedObject.new([{"b", 1}, {"a", 2}])
Enum.count(object)   #=> 2
Enum.into(object, %{}) #=> %{"a" => 2, "b" => 1}