ElixirConf 2016 - From Front-End to Full Stack with Elixir & Phoenix

ElixirConf 2016
From Front-End to Full Stack with Elixir & Phoenix
From Front-End
to Full Stack
With Elixir & Phoenix

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ElixirConf 2016
bit.ly/front-end-to-full-stack

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ElixirConf 2016
LAUREN TAN

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ElixirConf 2016

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ElixirConf 2016
! SUGARPIRATE_
" POTETO

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ElixirConf 2016
ZELDA

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ElixirConf 2016

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ElixirConf 2016
A long time ago in a galaxy
far, far away….

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ElixirConf 2016

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ElixirConf 2016
☠

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ElixirConf 2016

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ElixirConf 2016
JavaScript

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ElixirConf 2016
let foo = [1, 2, 3, 4, 5];
let bar = foo.map((n) => n + 1); // [2, 3, 4, 5, 6]
let baz = bar.filter((n) => n >=3 && n <= 5); // [3, 4, 5]
let qux = baz.reduce((n, el) => n += el); // 12
console.log(foo); // [1, 2, 3, 4, 5]

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ElixirConf 2016
let f = R.pipe(Math.pow, R.negate, R.inc);
f(3, 4); // -(3^4) + 1

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ElixirConf 2016

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ElixirConf 2016
MVC

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ElixirConf 2016
ember-changeset
https://github.com/DockYard/ember-changeset

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ElixirConf 2016
{{dummy-form
changeset=(changeset user EmployeeValidations)
submit=(action "submit")
rollback=(action "rollback")
}}

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ElixirConf 2016
https://facebook.github.io/react

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ElixirConf 2016
http://redux.js.org/

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ElixirConf 2016
I. Learn You Some Elixir for Great Good!
II. Phoenix is Not Rails
III.OOPs

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ElixirConf 2016
Elixir

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ElixirConf 2016

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ElixirConf 2016
https://www.youtube.com/watch?v=rRbY3TMUcgQ

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ElixirConf 2016
Domain Logic
Domain Logic
Domain Logic
Domain Logic
Web Umbrella App

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ElixirConf 2016
https://www.manning.com/books/elixir-in-action
https://www.manning.com/books/the-little-elixir-and-otp-guidebook

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ElixirConf 2016
|>i|>e

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ElixirConf 2016
foo(bar(baz(123), 456), 789)

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ElixirConf 2016
123
|> baz()
|> bar(456)
|> foo(123)

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ElixirConf 2016
Sugar?

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ElixirConf 2016
Small Functions

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ElixirConf 2016
def serialize(user) do
user
|> serialize_attributes()
|> serialize_relationships()
|> to_json()
end

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ElixirConf 2016
def validate_presence(input) do
if input == "" do
"Can't be blank"
end
input
end

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ElixirConf 2016
Pattern Matching

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ElixirConf 2016
def validate_presence(""), do: {:err, "Can't be blank"}
def validate_presence(input), do: input

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ElixirConf 2016
defmodule MyPlug do
import Plug.Conn
def init(opts), do: opts
def call(conn, currency: currency) do
case currency do
"USD" -> assign(conn, :greeting, "murica")
"CAD" -> assign(conn, :greeting, "eh?")
"AUD" -> assign(conn, :greeting, "oi mate")
_ -> conn
end
end
end

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ElixirConf 2016
defmodule MyPlug do
import Plug.Conn
def call(conn, currency: currency) do
greet(conn, currency)
end
def greet(conn, "USD"), do: assign(conn, :greeting, "murica")
def greet(conn, "CAD"), do: assign(conn, :greeting, "eh?")
def greet(conn, "AUD"), do: assign(conn, :greeting, "oi mate")
def greet(conn, _), do: conn
end

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ElixirConf 2016
defmodule WebhookMailer do
use Phoenix.Swoosh, view: MyApp.EmailView, layout: {MyApp.LayoutView, :email}
alias MyApp.User
def webhook(topic, %User{first_name: first_name, last_name: last_name, email: email}) do
title = title_for(topic)
new
|> to({"#{first_name} #{last_name}", email})
|> from({"Patrick", "[email protected]"})
|> subject(title)
|> render_body("webhook.html", %{title: title, first_name: first_name})
end
# ...
end

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ElixirConf 2016
defp title_for("customer_created"),
do: "Created account successfully"
defp title_for("customer_transfer_created"),
do: "Transfer created"
defp title_for("customer_transfer_cancelled"),
do: "Transfer cancelled"
defp title_for("customer_transfer_failed"),
do: "Transfer failed"
defp title_for("customer_transfer_completed"),
do: "Transfer completed"
defp title_for("customer_funding_source_added"),
do: "Funding source added"
defp title_for("customer_funding_source_removed"),
do: "Funding source removed"
defp title_for("customer_verified"),
do: "Your account was verified"
defp title_for("customer_suspended"),
do: "Your account was suspended"
defp title_for("customer_verification_documentation_needed"),
do: "Documentation needed"
defp title_for("customer_verification_documentation_uploaded"),
do: "Documentation uploaded"
defp title_for("customer_verification_documentation_approved"),
do: "Documentation approved"
defp title_for(message), do: message

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ElixirConf 2016
Recursion

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ElixirConf 2016
{
"id": "1",
"foo": {
"bar": {
"qux": "hello world"
},
"baz": 123
}
}

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ElixirConf 2016
defmodule Json do
def flatten(%{} = json) do
json
|> Map.to_list() # [foo: %{bar: %{qux: "hello world"}, baz: 123}, id: "1"]
|> to_flat_map(%{})
end
def flatten(%{} = json) when json == %{}, do: %{}
# ...
end

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ElixirConf 2016
bae's case

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ElixirConf 2016
defp to_flat_map([], acc), do: acc

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ElixirConf 2016
Add to accumulator

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ElixirConf 2016
defp to_flat_map([{_k, %{} = v} | t], acc) do
v
|> Map.to_list()
|> to_flat_map(to_flat_map(t, acc))
end

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ElixirConf 2016
Flatten all the things

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ElixirConf 2016
defp to_flat_map([{k, v} | t], acc) do
to_flat_map(t, Map.put_new(acc, k, v))
end

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ElixirConf 2016
%{id: "1", foo: %{bar: %{qux: "hello world"}, baz: 123}}
|> Json.flatten()
|> IO.inspect()
# %{baz: 123, id: "1", qux: "hello world"}

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ElixirConf 2016
defmodule Json do
def flatten(%{} = json) when json == %{}, do: %{}
def flatten(%{} = json) do
json
|> Map.to_list()
|> to_flat_map(%{})
end
defp to_flat_map([{_k, %{} = v} | t], acc), do: to_flat_map(Map.to_list(v), to_flat_map(t, acc))
defp to_flat_map([{k, v} | t], acc), do: to_flat_map(t, Map.put_new(acc, k, v))
defp to_flat_map([], acc), do: acc
end

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ElixirConf 2016
Data Types
https://engineering.appcues.com/2016/02/02/too-many-dicts.html

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ElixirConf 2016
Maps

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ElixirConf 2016
%{
"data" => %{
"type" => "articles",
"id" => "1"
}
}

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ElixirConf 2016

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ElixirConf 2016
%{
id: "1",
name: "Bob"
}

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ElixirConf 2016
Structs

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ElixirConf 2016
defmodule Employee do
@enforce_keys [:id]
defstruct id: nil, name: nil
@type t :: %Employee{id: pos_integer, name: String.t}
end
defmodule Team do
defstruct name: nil, employees: []
@type t :: %Team{name: String.t, employees: [Employee.t, ...]}
end

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ElixirConf 2016
defmodule Employee do
# ...
def promote(%Employee{salary: salary} = employee, pay_rise) do
%{employee | salary: round(salary * (1 + pct_increase))}
end
end
defmodule Team do
# ...
def promote_all(%Team{employees: employees}, bonus) do
Enum.map(employees, &(Employee.promote(&1, bonus)))
end
end

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ElixirConf 2016
bob = %Employee{id: "1", name: "Bob", salary: 80_000}
jane = %Employee{id: "2", name: "Jane", salary: 100_000}
team = %Team{name: "Accounting", employees: [bob, jane]}
# %Team{employees: [%Employee{id: "1", name: "Bob", salary: 80000},
# %Employee{id: "2", name: "Jane", salary: 100000}], name: "Accounting"}
Team.promote_all(team, 0.2) # 20% pay rise
# [%Employee{id: "1", name: "Bob", salary: 96000},
# %Employee{id: "2", name: "Jane", salary: 120000}]

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ElixirConf 2016
Tuples

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{:ok, result}

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ElixirConf 2016
{:ok, result}
{:err, "message"}

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ElixirConf 2016
defmodule Foo do
def serialize(user) do
with {:ok, serialized} <- serialize_attributes(user),
{:ok, serialized} <- serialize_relationships(serialized),
do: to_json(serialized)
end
def serialize_attributes(user), do: {:ok, user}
def serialize_relationships(user), do: {:ok, user}
def to_json(map), do: Poison.encode!(map)
end

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ElixirConf 2016
Keywords

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ElixirConf 2016
def to_currency(value, currency: "USD", cents?: cents?), do: # ...

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ElixirConf 2016
Protocols

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ElixirConf 2016
defmodule Team do
# ...
defimpl Enumerable do
def count(%Team{employees: employees}), do: {:ok, length(employees)}
end
end

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ElixirConf 2016
team
# %Team{employees: [%Employee{id: "1", name: "Bob", salary: 80000},
# %Employee{id: "2", name: "Jane", salary: 100000}], name: "Accounting"}
Enum.count(team)
# 2

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ElixirConf 2016
defmodule Team do
# ...
defimpl Enumerable do
def count(%Team{employees: employees}), do: {:ok, length(employees)}
def member?(_, _), do: {:error, __MODULE__}
def reduce(%Team{employees: employees}, acc, fun), do: do_reduce(employees, acc, fun)
# default list reducer
defp do_reduce(_, {:halt, acc}, _fun), do: {:halted, acc}
defp do_reduce(list, {:suspend, acc}, fun), do: {:suspended, acc, &do_reduce(list, &1, fun)}
defp do_reduce([], {:cont, acc}, _fun), do: {:done, acc}
defp do_reduce([h | t], {:cont, acc}, fun), do: do_reduce(t, fun.(h, acc), fun)
end
end

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ElixirConf 2016
bob = %Employee{id: "1", name: "Bob", salary: 10_000}
jane = %Employee{id: "2", name: "Jane", salary: 20_000}
team = %Team{name: "Accounting", employees: [bob, jane]}
Enum.member?(team, bob)
# true
Enum.map(team, fn e -> e.name end)
# ["Bob", "Jane"]
Enum.max_by(team, fn e -> e.salary end)
# %Employee{id: "2", name: "Jane", salary: 20000}

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ElixirConf 2016
defmodule Team do
# ...
def promote_all(%Team{employees: employees}, bonus) do
Enum.map(employees, &(Employee.promote(&1, bonus)))
end
end

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ElixirConf 2016
defmodule Team do
# ...
def promote_all(%Team{} = team, bonus) do
Enum.map(team, &(Employee.promote(&1, bonus)))
end
end

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ElixirConf 2016
Behaviours

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ElixirConf 2016
Interface

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ElixirConf 2016
defmodule Request do
defstruct headers: %{}, body: %{}
end

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ElixirConf 2016
defmodule Validator do
@callback validate(request :: Request.t, attribute :: :atom) :: %{}
@callback valid?(value :: any) :: boolean
@optional_callbacks valid?: 1
end

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ElixirConf 2016
defmodule Validator.Presence do
@behaviour Validator
def validate(%Request{body: body}, attribute) do
valid?(Map.get(body, attribute))
end
def valid?(nil), do: false
def valid?(%{} = map) when map === %{}, do: false
def valid?([]), do: false
def valid?(_), do: true
end

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ElixirConf 2016
warning: undefined behaviour function validate/2 (for behaviour Validator)
lib/examples/behaviours.ex:10
warning: undefined behaviour function valid?/1 (for behaviour Validator)
lib/examples/behaviours.ex:10

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ElixirConf 2016
# behaviours.ex:15: The call 'Elixir.Map':get(body@1::[],attribute@1::any()) will
# never return since the success typing is (map(),any()) -> any()
# and the contract is (map(),key()) -> value()

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ElixirConf 2016
$ mix dialyzer
https://github.com/jeremyjh/dialyxir

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ElixirConf 2016
@spec
https://medium.com/@barruumrex/seeking-simple-satisfaction-2a098902ddff

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ElixirConf 2016
Macros

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ElixirConf 2016

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ElixirConf 2016
Elixir is written in Elixir

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ElixirConf 2016

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ElixirConf 2016
elixir/lib/elixir/src/elixir_bootstrap.erl

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ElixirConf 2016
# Use elixir_bootstrap module to be able to bootstrap Kernel.
# The bootstrap module provides simpler implementations of the
# functions removed, simple enough to bootstrap.
import Kernel, except: [@: 1, defmodule: 2, def: 1, def: 2, defp: 2,
defmacro: 1, defmacro: 2, defmacrop: 2]
import :elixir_bootstrap
defmodule Kernel do
# ...
end

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ElixirConf 2016
Erlang compiles Elixir

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ElixirConf 2016
-export(['MACRO-def'/2, 'MACRO-def'/3, 'MACRO-defp'/3, 'MACRO-defmodule'/3,
'MACRO-defmacro'/2, 'MACRO-defmacro'/3, 'MACRO-defmacrop'/3,
'MACRO-@'/2, '__info__'/1]).

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ElixirConf 2016

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ElixirConf 2016
Kernel.SpecialForms

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ElixirConf 2016
defmacro unquote(:%{})(args), do: error!([args])

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ElixirConf 2016
expand({'%{}', Meta, Args}, E) ->
elixir_map:expand_map(Meta, Args, E);

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ElixirConf 2016
expand_map(Meta, [{'|', UpdateMeta, [Left, Right]}], E) ->
{[ELeft | ERight], EA} = elixir_exp:expand_args([Left | Right], E),
validate_kv(Meta, ERight, Right, E),
{{'%{}', Meta, [{'|', UpdateMeta, [ELeft, ERight]}]}, EA};
expand_map(Meta, Args, E) ->
{EArgs, EA} = elixir_exp:expand_args(Args, E),
validate_kv(Meta, EArgs, Args, E),
{{'%{}', Meta, EArgs}, EA}.

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ElixirConf 2016
:math.pi
# 3.141592653589793

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ElixirConf 2016
:maps.new() === %{}
# true

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ElixirConf 2016
defmodule CowSay do
defmacro __using__(_) do
quote do
def cowsay(str) do
"""
#{make_line("_", String.length(str))}
< #{str} >
#{make_line("-", String.length(str))}
\\ ^__^
\\ (oo)\\_______
(__)\\ )\\/\\
||----w |
|| ||
"""
|> IO.puts()
end
defp make_line(char, len), do: String.duplicate(char, len + 1)
end
end
end

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ElixirConf 2016
defmodule Bob do
use CowSay
end
Bob.cowsay("It's me Bob")

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ElixirConf 2016
https://pragprog.com/book/cmelixir/metaprogramming-elixir

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ElixirConf 2016
III.OOPs

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ElixirConf 2016

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ElixirConf 2016
Pipelines

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ElixirConf 2016
lib/my_app/endpoint.ex

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ElixirConf 2016
conn

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ElixirConf 2016
conn
conn
Endpoint
Router Controller
DB
Pipeline
200 OK
Ecto
View

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ElixirConf 2016
Phoenix is a pipeline

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ElixirConf 2016
Composed of pipelines

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ElixirConf 2016
Made out of plugs

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ElixirConf 2016
And functions

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ElixirConf 2016
Plug

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ElixirConf 2016

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ElixirConf 2016
def my_plug(conn, _opts) do
conn
end

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ElixirConf 2016
defmodule MyApp.Authorization do
import Plug.Conn
def call(conn, opts) do
# ...
end
end

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ElixirConf 2016
defmodule MyApp.Router do
use MyApp.Web, :router
pipeline :authorized do
plug MyApp.Authorization
end
scope "/api", MyApp do
pipe_through :authorized
scope "/v1", Api.V1 do
get "/status", StatusController, :index
end
end
end

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ElixirConf 2016
defmodule MyApp.WebhookController do
use MyApp.Web, :controller
plug :verify_request_signature
def create(conn, # ...) do
# ...
end
defp verify_request_signature(conn, _) do
# ...
end
end

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ElixirConf 2016
pipeline :json_api do
plug :accepts, ["json", "json-api"]
plug :fetch_session
plug JaSerializer.ContentTypeNegotiation
plug JaSerializer.Deserializer
end

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ElixirConf 2016
scope "/api", MyApp do
pipe_through :json_api
# public routes
get "/foo", FooController, :index
scope "/v1", Api.V1 do
pipe_through :authorized
resources "/users", UserController: only: [:index, :show]
end
end

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ElixirConf 2016
lib/my_app/endpoint.ex

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ElixirConf 2016
defmodule MyApp.Endpoint do
use Phoenix.Endpoint, otp_app: :my_app
socket "/socket", MyApp.UserSocket
plug Plug.Static,
at: "/", from: :my_app, gzip: false,
only: ~w(css fonts images js favicon.ico robots.txt)
if code_reloading? do
plug Phoenix.CodeReloader
end
plug Plug.RequestId
plug Plug.Logger
plug Plug.Parsers,
parsers: [:urlencoded, :multipart, :json],
pass: ["*/*"],
json_decoder: Poison
plug Plug.MethodOverride
plug Plug.Head
plug Plug.Session,
store: :cookie,
key: "_my_app_key",
signing_salt: "BKi/ZZMd"
plug MyApp.Router
end

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ElixirConf 2016
Fractal

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ElixirConf 2016
Terraform
https://github.com/poteto/terraform

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ElixirConf 2016
Incremental Phoenix

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ElixirConf 2016
iex(1)> [info] GET /v1/foo
[debug] Processing by MyApp.FooController.index/2
Parameters: %{}
Pipelines: [:api]
[info] Sent 200 in 22ms
[info] GET /v1/bar
[debug] Processing by MyApp.BarController.index/2
Parameters: %{}
Pipelines: [:api]
[info] Sent 200 in 116µs
[info] GET /v1/hello-world # forwarded to legacy API
[info] GET /v1/gifs/search # forwarded to legacy API

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ElixirConf 2016
defmodule MyApp.Endpoint do
# ...
plug MyApp.ForwardRequest,
client: MyApp.Forwarders.Giphy,
router: MyApp.Router
plug MyApp.Router
end

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ElixirConf 2016
defmodule MyApp.ForwardRequest do
import Plug.Conn
def call(conn, client: client, router: router) do
routes = router.__routes__ #
conn
|> match_route(routes)
|> handle_request(client)
|> send_response()
end
# ...
end

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ElixirConf 2016
defmacro __before_compile__(_env) do
quote location: :keep do
defoverridable [call: 2]
try do
super(conn, opts)
catch
kind, reason ->
Plug.ErrorHandler.__catch__(conn, kind, reason, &handle_errors/2)
end
end
end
end

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ElixirConf 2016
catch
kind, reason ->
# do our forward here
end

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ElixirConf 2016
Terraform
https://github.com/poteto/terraform

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ElixirConf 2016
defmodule Terraform do
defmacro __using__(opts) do
Module.register_attribute __MODULE__, :terraformer, []
@terraformer Keyword.get(unquote(opts), :terraformer)
@before_compile Terraform
end
end
# ...
end

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ElixirConf 2016
defmacro __before_compile__(_env) do
defoverridable [call: 2]
try do
super(conn, opts)
catch
_, %{conn: conn} -> terraform(conn, @terraformer)
end
end
defp terraform(conn, terraformer) do
terraformer.call(conn, [])
end
defoverridable [terraform: 2]
end
end

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ElixirConf 2016
defmodule MyApp.Router do
use Terraform, terraformer: MyApp.Terraformers.Foo
# ...
end

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ElixirConf 2016
defmodule MyApp.Terraformers.Foo do
alias MyApp.Clients.Foo # example client made with HTTPoison
use Plug.Router
plug :match
plug :dispatch
# match specific path
get "/v1/hello-world", do: send_resp(conn, 200, "Hello world")
# match all `get`s
get _ do
%{method: "GET", request_path: request_path, params: params, req_headers: req_headers} = conn
res = Foo.get!(request_path, req_headers, [params: Map.to_list(params)])
send_response({:ok, conn, res})
end
def send_response({:ok, conn, %{headers: headers, status_code: status_code, body: body}}) do
conn = %{conn | resp_headers: headers}
send_resp(conn, status_code, body)
end
end

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ElixirConf 2016
III.OOPs

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Design Patterns

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–Sandi Metz
“Duplication is far cheaper than
the wrong abstraction.”

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https://fsharpforfunandprofit.com/fppatterns/

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State

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ElixirConf 2016
Objects

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ElixirConf 2016
class Person {
constructor(name) {
this.name = name;
this.x = 0;
this.y = 0;
}
greet() {
return `Hi there, my name is ${this.name}.`;
}
report() {
return `I'm at (${this.x}, ${this.y}).`;
}
move(x = 0, y = 0) {
this.x = x;
this.y = y;
}
}

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ElixirConf 2016
let bob = new Person('Bob');
bob.greet(); // "Hi there, my name is Bob."
bob.report(); // "I'm at (0, 0)."

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bob.move(1, 2);
bob.report(); // "I'm at (1, 2)."

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ElixirConf 2016
class Movable {
constructor(x, y) {
this.move(x, y);
}
move(x = 0, y = 0) {
this.x = x;
this.y = y;
}
report() {
return `I'm at (${this.x}, ${this.y}).`;
}
}

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ElixirConf 2016
class Person extends Movable {
constructor(name) {
super();
this.name = name;
}
greet() {
return `Hi there, my name is ${this.name}.`;
}
}

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ElixirConf 2016
Data

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ElixirConf 2016
Function

apple -> banana

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ElixirConf 2016
.toBanana();

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.toPineapple();

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ElixirConf 2016
Uncaught TypeError: .toPineapple is not a function(…)

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ElixirConf 2016

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ElixirConf 2016

Function

apple -> banana
Function
banana -> pineapple

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ElixirConf 2016

Function

apple -> banana
Function
banana -> pineapple

Composition

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ElixirConf 2016
Function

apple -> pineapple

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ElixirConf 2016
Model the System

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ElixirConf 2016
Transform the Data

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ElixirConf 2016
Fractal

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ElixirConf 2016
Function
input output

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ElixirConf 2016
low level operation low level operation low level operation
EmailValidator
Service
email validated result

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ElixirConf 2016
service service service
UpdateProfile
Use-case
change profile
request
change profile
result

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ElixirConf 2016
use-case use-case use-case
Web Application
http request http response

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ElixirConf 2016 - From Front-End to Full Stack with Elixir & Phoenix

ElixirConf 2016 - From Front-End to Full Stack with Elixir & Phoenix

Lauren Tan

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