Protocols and Structs

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!