Introduction to Elixir and Phoenix.pdf

1. Introduction to Elixir and
Phoenix
Created by Ridwan Fadjar Septian,
At SenseHealth B.V.
Bandung, 26th September 2018

2. Disclaimer
- I am just curious about Elixir and Phoenix Web Framework for personal usage only
- Currently I don’t have an experience using Elixir in production
- I bought Elixir and Phoenix course on Udemy for my hobby
- Alam embrace me to learn Elixir and set up a sharing session

3. Background and Motivation
Why Elixir?

4. Elixir at Glance
Fundamental

5. Hello world
iex > IO.puts("hello world!")
hello world!
:ok

6. Data Type
iex> 255
255
iex> 0b0110
6
iex> 0o644
420
iex> 0x1F
31
iex> 3.14
3.14
iex> 1.0e-10
1.0e-10
iex> true
true
iex> false
False

7. Data Type
iex> :foo
:foo
iex> :foo == :bar
false
iex> "Hello"
"Hello"
iex> "さようなら"
"さようなら"
iex> "foo
...> bar"
"foonbar"
iex> "foonbar"
"foonbar"

8. Basic Operator
iex> 2 + 2
4
iex> 2 - 1
1
iex> 2 * 5
10
iex> 10 / 5
2.0
iex> div(10, 5)
2
iex> rem(10, 3)
1

9. Basic Operator
iex> -20 || true
-20
iex> false || 42
42
iex> 42 && true
true
iex> 42 && nil
nil
iex> !42
false
iex> !false
true

10. Basic Operator
iex> true and 42
42
iex> false or true
true
iex> not false
true
iex> 1 > 2
false
iex> 1 != 2
true
iex> 2 == 2
true
iex> 2 <= 3
true
iex> 2 == 2.0
true
iex> 2 === 2.0
false

11. Basic Operator
iex> "Elixir rocks" |> String.upcase() |> String.split()
["ELIXIR", "ROCKS"]

12. Conditional
iex> if String.valid?("Hello") do
...> "Valid string!"
...> else
...> "Invalid string."
...> end
"Valid string!"
iex> if "a string value" do
...> "Truthy"
...> end
"Truthy"

13. Conditional
iex> unless is_integer("hello") do
...> "Not an Int"
...> end
"Not an Int"

14. Conditional
iex> case {:ok, "Hello World"} do
...> {:ok, result} -> result
...> {:error} -> "Uh oh!"
...> _ -> "Catch all"
...> end
"Hello World"

15. Conditional
iex> cond do
...> 2 + 2 == 5 ->
...> "This will not be true"
...> 2 * 2 == 3 ->
...> "Nor this"
...> 1 + 1 == 2 ->
...> "But this will"
...> end
"But this will"

16. Recursion
defmodule Loop do
def print_multiple_times
(msg, n) when n <= 1 do
IO.puts msg
end
def print_multiple_times
(msg, n) do
IO.puts msg
print_multiple_times
(msg, n - 1)
end
end
Loop.print_multiple_times
("Hello", 10)

17. Function
iex> sum = fn (a, b) -> a + b end
iex> sum.(2, 3)
5
iex> sum = &(&1 + &2)
iex> sum.(2, 3)
5

18. Function and Module
defmodule Greeter do
def hello(name) do
"Hello, " <> name
end
end
iex> Greeter.hello("Sean")
"Hello, Sean"

19. Function and Module
defmodule Greeter2 do
def hello(), do: "Hello, anonymous person!" # hello/0
def hello(name), do: "Hello, " <> name # hello/1
def hello(name1, name2), do: "Hello, #{name1} and #{name2}"
# hello/2
end
iex> Greeter2.hello()
"Hello, anonymous person!"
iex> Greeter2.hello("Fred")
"Hello, Fred"
iex> Greeter2.hello("Fred", "Jane")
"Hello, Fred and Jane"

20. Mix
Package Manager in Elixir

21. Phoenix
Web Framework for Elixir

22. Getting Started
$ mix archive.install
https://github.com/phoenixframework/archives/raw/master/phx_new.ez
$ mix phx.new tracking-api --app my_app --module TrackingAPI --no-brunch --no-html
$ cd tracking-api
$ mix phx.server

23. Supported Database
- PostgreSQL
- MySQL

24. Configs
use Mix.Config
config :tracking_api, TrackingAPIWeb.Endpoint,
http: [port: 4000],
debug_errors: false,
code_reloader: true,
check_origin: false,
watchers: []
config :logger, :console, format: "[$level] $messagen"
config :phoenix, :stacktrace_depth, 20
config :tracking_api, TrackingAPI.Repo,
adapter: Ecto.Adapters.Postgres,
username: "phoenix",
password: "phoenix",
database: "tracking_api_dev",
hostname: "localhost",
pool_size: 10

25. Models
schema "gps_tracking" do
field :application_id, Ecto.UUID
field :created_at, :utc_datetime
field :latitude, :string
field :longitude, :string
field :user_id, Ecto.UUID
timestamps()
end
@doc false
def changeset(gps_tracking, attrs) do
gps_tracking
|> cast(attrs, [:application_id, :user_id, :latitude, :longitude, :created_at])
|> validate_required([:application_id, :user_id, :latitude, :longitude, :created_at])
end

26. Repo
def list_gps_tracking do
Repo.all(GPSTracking)
end
def get_gps_tracking!(id), do: Repo.get!(GPSTracking, id)
def create_gps_tracking(attrs %{}) do
%GPSTracking{}
|> GPSTracking.changeset(attrs)
|> Repo.insert()
end
def update_gps_tracking(%GPSTracking{} = gps_tracking, attrs) do
gps_tracking
|> GPSTracking.changeset(attrs)
|> Repo.update()
end
def delete_gps_tracking(%GPSTracking{} = gps_tracking) do
Repo.delete(gps_tracking)
end
def change_gps_tracking(%GPSTracking{} = gps_tracking) do
GPSTracking.changeset(gps_tracking, %{})
end

27. Controllers
defmodule TrackingAPIWeb.GPSTrackingController do
use TrackingAPIWeb, :controller
alias TrackingAPI.Tracking
alias TrackingAPI.Tracking.GPSTracking
action_fallback TrackingAPIWeb.FallbackController
def index(conn, _params) do
gps_tracking = Tracking.list_gps_tracking()
render(conn, "index.json", gps_tracking: gps_tracking)
end
def create(conn, %{"gps_tracking" => gps_tracking_params}) do
with {:ok, %GPSTracking{} = gps_tracking} <- Tracking.create_gps_tracking(gps_tracking_params) do
conn
|> put_status(:created)
|> put_resp_header("location", gps_tracking_path(conn, :show, gps_tracking))
|> render("show.json", gps_tracking: gps_tracking)
end
end
end

28. We cannot use update endpoint! We exclude it.

29. Views
def render("index.json", %{gps_tracking: gps_tracking}) do
%{data: render_many(gps_tracking, GPSTrackingView, "gps_tracking.json")}
end
def render("show.json", %{gps_tracking: gps_tracking}) do
%{data: render_one(gps_tracking, GPSTrackingView, "gps_tracking.json")}
end
def render("gps_tracking.json", %{gps_tracking: gps_tracking}) do
%{id: gps_tracking.id,
application_id: gps_tracking.application_id,
user_id: gps_tracking.user_id,
latitude: gps_tracking.latitude,
longitude: gps_tracking.longitude,
created_at: gps_tracking.created_at}
end

30. Router
defmodule TrackingAPIWeb.Router do
use TrackingAPIWeb, :router
pipeline :api do
plug :accepts, ["json"]
end
scope "/api", TrackingAPIWeb do
pipe_through :api
resources "/gps_tracking", GPSTrackingController, except: [:edit]
end
end

31. Testing
test "list_gps_tracking/0 returns all gps_tracking" do
gps_tracking = gps_tracking_fixture()
assert Tracking.list_gps_tracking() == [gps_tracking]
end
test "get_gps_tracking!/1 returns the gps_tracking with given id" do
gps_tracking = gps_tracking_fixture()
assert Tracking.get_gps_tracking!(gps_tracking.id) == gps_tracking
end
test "create_gps_tracking/1 with valid data creates a gps_tracking" do
assert {:ok, %GPSTracking{} = gps_tracking} = Tracking.create_gps_tracking(@valid_attrs)
assert gps_tracking.application_id == "7488a646-e31f-11e4-aace-600308960662"
assert gps_tracking.created_at == DateTime.from_naive!(~N[2010-04-17 14:00:00.000000Z], "Etc/UTC")
assert gps_tracking.latitude == "some latitude"
assert gps_tracking.longitude == "some longitude"
assert gps_tracking.user_id == "7488a646-e31f-11e4-aace-600308960662"
end
test "create_gps_tracking/1 with invalid data returns error changeset" do
assert {:error, %Ecto.Changeset{}} = Tracking.create_gps_tracking(@invalid_attrs)
end

32. References
- https://hexdocs.pm/phoenix/
- https://elixirschool.com/
- https://www.tutorialspoint.com/elixir/
- https://elixir-lang.org/docs.html
- https://github.com/h4cc/awesome-elixir
- https://github.com/droptheplot/awesome-phoenix

33. Demo