An intro to Elixir

At a Deliveroo internal conference I gave a quick intro to Elixir.

Transcript

1. An intro to Elixir
2. A is not a Sandwich
3. This talk - About Me - wtf is Elixir - Basics - Cool in Elixir - Phoenix
4. I’m Tommy
5. I’m Tommy - ~3 years @ Deliveroo
6. I’m Tommy - ~3 years @ Deliveroo - Ruby for ~10 years
7. I’m Tommy - ~3 years @ Deliveroo - Ruby for ~10 years - Elixir for ~2 years
8. I’m Tommy - ~3 years @ Deliveroo - Ruby for ~10 years - Elixir for ~2 years - I know that I look like Tormund Giantsbane
9. wtf is Elixir?
10. wtf is Elixir? Elixir is a dynamic, functional language designed for building scalable and maintainable applications.
11. wtf is Elixir? - Created in 2012 by José Valim (former Rails Core Team)
12. wtf is Elixir? - Created in 2012 by José Valim (former Rails Core Team) - Built on top of, and compiles to, Erlang
13. wtf is Elixir? - Created in 2012 by José Valim (former Rails Core Team) - Built on top of, and compiles to, Erlang - Functional
14. wtf is Elixir? - Created in 2012 by José Valim (former Rails Core Team) - Built on top of, and compiles to, Erlang - Functional - Built with distributed resiliency in mind
15. Built on top of Erlang
16. Built on top of Erlang - Made by Ericsson in 1986
17. Built on top of Erlang - Made by Ericsson in 1986 - Erlang runs:
18. Built on top of Erlang - Made by Ericsson in 1986 - Erlang runs: - WhatsApp
19. Built on top of Erlang - Made by Ericsson in 1986 - Erlang runs: - WhatsApp - Facebook Messanger
20. Built on top of Erlang - Made by Ericsson in 1986 - Erlang runs: - WhatsApp - Facebook Messanger - SMS
21. Built on top of Erlang - Made by Ericsson in 1986 - Erlang runs: - WhatsApp - Facebook Messanger - SMS - GPRS and 3G networks
22. Built on top of Erlang - Made by Ericsson in 1986 - Erlang runs: - WhatsApp - Facebook Messanger - SMS - GPRS and 3G networks - Lots of Online Gaming
23. You’ve probably interacted with Erlang today and didn’t even know it
24. Erlang: The Movie
25. Erlang: The Moustache
26. Erlang’s pretty old, so why isn’t it more popular?
27. * OTP means Open Telephony Platform * Erlang/OTP is run by Ericsson * the syntax is prolog-y & not c-y or ruby-y or python-y, its just too damn erlang-y * no package manager * no list of open source packages * no community site * the mailing list is the community * everyone knows each other from Stockholm * it is too hard to get a first working app * lists for strings, aargh! * no for loops, eek! * variables don't vary, whimper! * people don't learn OTP first but start with Erlang * people don't learn Erlang first but start with OTP * no docs * too many docs but it is the wrong sort * not enough teaching materials * doesn't run on the JVM * we used to think that it was because there were no books... * Erlang Solutions isn't a proper internet company * the language develops too slowly * emacs is the IDE
28. Elixir fixes these problems
29. Basics
30. Functional No objects! Modules, functions and arguments. Module.Module.function(arg)
31. Distributed resiliency - Elixir is a multi-core language - State is held in lightweight Elixir processes - Processes can start, run, crash and restart easily
32. Distributed resiliency Supervisor Process Supervisor Process Supervisor Process Worker Process Worker Process Worker Process Worker Process
33. Distributed resiliency Supervisor Process Supervisor Process Supervisor Process Worker Process Worker Process Worker Process Worker Process
34. Distributed resiliency Supervisor Process Supervisor Process Supervisor Process Worker Process Worker Process Worker Process
35. Distributed resiliency Supervisor Process Supervisor Process Supervisor Process Worker Process Worker Process Worker Process Worker Process
36. Let it crash and allow your system to recover
37. Cool in Elixir
38. Equals is not equals > a = 2 2
39. Equals is pattern match > [1, 2, val] = [1, 2, 3] > val 3
40. Equals is pattern match > [2, 4, val] = [1, 2, 3] ** (MatchError) no match of right hand side value: [1, 2, 3]
41. Pattern matching a Tuple > {:hello, value} = {:hello, "world"} > value “world"
42. Pattern matching a Tuple case ApiFetcher.fetch(url) do {:ok, body} -> # Do something with `body` {:error, error} -> # Do something with `error` end
43. defmodule Text do def to_upcase(arg) do String.upcase(arg) end end > Text.to_upcase("hello") "HELLO" Defining functions
44. defmodule Formatter do def format("up:" <> username) do String.upcase(username) end def format(“reverse:" <> title) do String.reverse(title) end end Defining multiple versions of the same function
45. > Formatter.format("up:hello") "HELLO" > Formatter.format(“reverse:world") "dlrow" Defining multiple versions of the same function
46. defmodule Numbers do def double(arr) do Enum.map(arr, fn(x) -> x * 2 end) end end > Numbers.double([1, 2, 3]) [2, 4, 6] Loops
47. Pipes
48. defmodule Formatter do def format(data) do Map.get(data, :warning) |> String.upcase |> String.reverse end end > Formatter.format(%{warning: "murder"}) "REDRUM" Pipes
49. defmodule Formatter do def format(data) do Map.get(data, :warning) |> String.upcase |> String.reverse end end Pipes
50. defmodule Formatter do def format(data) do data |> Map.get(:warning) |> String.upcase |> String.reverse end end Pipes
51. def publish(%Post{status: status}) when status == :draft do # Publish a post end > Publisher.publish(%Post{status: :published}) ** (FunctionClauseError) no function clause matching in Publisher.publish/1 The following arguments were given to Publisher.publish/1: # 1 %Post{status: :published} Guards
52. GenServer Concurrently holding state in an Elixir Process
53. defmodule Basket do use GenServer def init(items) do {:ok, item} end def handle_call(:pop, _from, [head | tail]) do {:reply, head, tail} end def handle_cast({:push, item}, state) do {:noreply, [item | state]} end end GenServer
54. > {:ok, pid} = GenServer.start_link(Basket, [:burger]) {:ok, #PID<0.354.0>} > GenServer.call(pid, :pop) :burger > GenServer.cast(pid, {:push, :fries}) :ok > GenServer.call(pid, :pop) :fries GenServer
55. Phoenix
56. Phoenix - A Rails like web framework for Elixir - Controllers - Views (like Presenters) - Templates with Embedded Elixir (.eex) - Ecto (for DB interaction, like Active Record) - WebSockets - Contexts
57. WebSockets Phoenix has Channels
58. defmodule ChatWeb.ChatChannel do use Phoenix.Channel def join("chat:lobby", _message, socket) do {:ok, socket} end def join("chat:" <> room_id, _params, socket) do socket = assign(socket, :room_id, room_id) {:ok, socket} end def handle_in("join_room", %{"username" => username}, socket) do body = %{ new_user: username } broadcast!(socket, “new_user”, %{body: body}) {:noreply, socket} end end Channels
59. import {Socket} from "phoenix" let socket = new Socket("ws://localhost:4000/socket") socket.connect() let channel = socket.channel("room:lobby", {}) channel.join() channel.on("new_user", (body) => { console.log("New user!", body.user) }) Channels
60. Without models, where do we put our code?
62. Contexts help us organise our code
64. Conclusion
65. Elixir is good Phoenix is good
68. {:ok, :finish}
69. Further reading - elixir-lang.com - phoenixframework.org - github.com/h4cc/awesome-elixir - #elixir-lang on Deliveroo Slack - We’re hosting London Elixir on Tuesday