Protocols and Structs

Processing a data flow in Elixir

Transcript

1. PROTOCOLS AND STRUCTS FOR EFFECTIVE DATA FLOW
2. THE DOMAIN CHECK-IN PROCESS NOTIFY
3. RECAP ABOUT PROTOCOLS AND STRUCTS
4. STRUCTS defmodule Checkin do defstruct id: nil, lat: 0.0, lng: 0.0 end
5. STRUCTS %Checkin{id: "123", lat: 51.50, lng: 0.12} struct(Checkin, id: "123", lat: 51.50, lng: 0.12) struct(Checkin, %{id: "123", lat: 51.50, lng: 0.12}) struct(Checkin, id: "123", lat: 51.50, lng: 0.12, ignored: true)
6. PROTOCOLS defprotocol Persistence do def create(thing) end
7. IMPLEMENTATION defimpl Persistence, for: Checkin do def create(checkin) do %Doc{class: "Checkin", fields: Map.from_struct(checkin)} |> Repo.create end end
8. FALLBACK defprotocol Persistence do @fallback_to_any true def create(thing) end
9. FALLBACK defimpl Persistence, for: Any do def create(thing) do class = Map.get(thing, :__struct__) |> to_string %Doc{class: class, fields: Map.from_struct(thing)} |> Repo.create end end
10. USAGE %Checkin{id: "123", lat: 51.50, lng: 0.12} |> Persistence.create
11. FLOW MESSAGE IDENTIFY LOG PROCESS LOG NOTIFY
12. FLOW MESSAGE IDENTIFY LOG PROCESS LOG NOTIFY
13. IDENTIFY { "meta" : { "version" : 1, "topic" : "checkins", "type" : "create", "request_id" : "15456d4e-782b-11e5-8bcf-feff819cdc9f" }, "data" : { "ref" : "123ASDS", "lat" : 51.50, "lng" : 0.12 } }
14. IDENTIFY defmodule V1.Checkin.Create do defstruct request_id: nil, ref: nil, lat: 0.0, lng: 0.0 end
15. IDENTIFY def identify(payload) do case payload["meta"] do %{"version" => 1, "topic" => "checkins", "type" => "create"} -> V1.Checkins.Create _other -> {:error, :unsupported_payload} end end
16. POPULATE def populate(struct_name, payload) do request_id = get_in(payload, "meta", "request_id") struct_attrs = Map.put(payload["data"], "request_id", request_id) Kernel.struct(struct_name, Utils.atomise_map(struct_attrs)) end
17. ALL TOGETHER NOW message |> identify |> populate(message)
18. WINS STABLE INTERFACE DEFINES A BOUNDARY EXTENSIBLE INTENTION REVEALING
19. FLOW MESSAGE IDENTIFY LOG PROCESS LOG NOTIFY
20. LOG defimpl String.Chars, for: V1.Checkins.Create do def to_string(create_struct) do "type=create status=accepted request_id=#{create_struct.request_id} ref={create_struct.ref}" end end
21. LOG def log(item) do :ok = Logger.info item item end
22. ALL TOGETHER NOW message |> identify |> populate(message) |> log
23. FLOW MESSAGE IDENTIFY LOG PROCESS LOG NOTIFY
24. PROCESS defimpl Job, for: V1.Checkin.Create do def process(create_struct) do {:ok, new_record} = Persistence.create(create_struct) %V1.Checkin.Created{request_id: create_struct.request_id, record: new_record} end end
25. ALL TOGETHER NOW message |> identify |> populate(message) |> log |> Job.process
26. WINS STABLE INTERFACE DEFINES A BOUNDARY EXTENSIBLE INTENTION REVEALING
27. FLOW MESSAGE IDENTIFY LOG PROCESS LOG NOTIFY
28. LOG defimpl String.Chars, for: V1.Checkins.Created do def to_string(created_struct) do "type=create status=processed request_id=#{create_struct.request_id} id={created_struct.record.id}" end end
29. ALL TOGETHER NOW message |> identify |> populate(message) |> log |> Job.process |> log
30. NOTIFY MESSAGE IDENTIFY LOG PROCESS LOG NOTIFY
31. NOTIFY defimpl Notify, for: V1.Checkin.Created do def topics(created_struct), do: ["checkins", "users"] def to_message(created_struct) do %Message{request_id: created_struct.request_id, type: :create, data: %{id: created_struct.record.id}} end end
32. NOTIFY def notify(item) do payload = Notify.to_message(item) topics = Notify.topics(item) PubSub.broadcast(payload, topics) end
33. ALL TOGETHER NOW message |> identify |> populate(message) |> log |> Job.process |> log |> notify
34. EXECUTION MESSAGE IDENTIFY LOG PROCESS LOG NOTIFY LISTENER PROCESS POOL PUBSUB POOL
35. EXTENDING FURTHER ADD NEW STRUCTS IMPLEMENT PROTOCOLS
36. CORE IDEAS ASSIGN INTENT TO DATA DEFINE FUNCTIONALITY AS PROTOCOLS DEFINE STRICT BOUNDARIES BETWEEN STEPS
37. THANK YOU! http://bit.ly/ff-protocols-structs
38. PLUG ELIXIR, JAVASCRIPT, ELM DEVELOPMENT ELIXIR, JAVASCRIPT, ELM TRAINING ASK ME ABOUT IT!