PragTob

  def create(order_params, customer, auth) do
    with {:ok, order} <- validate_order(order_params, customer),
         {:ok, order} <- validate_tour_shipment_in_backend(order, auth),
         {:ok, order} <- Repo.insert(order) do
      {:ok, order}
    else
      {:error, changeset} -> {:error, changeset}
    end
  end

PragTob

  @doc """
  ## Examples

      iex> {:ok, pid} = Agent.start_link(fn -> 42 end)
      iex> Agent.get_and_update(pid, fn(state) -> {state, state + 1} end)
      42
      iex> Agent.get(pid, fn(state) -> state end)
      43
  """

PragTob

  @type job_name :: String.t | atom
  
  @spec benchmark(Suite.t, job_name, fun, module) :: Suite.t
  def benchmark(suite = %Suite{scenarios: scenarios}, job_name, function, printer \\ Printer) do
    #...
  end

PragTob

def new_changeset(model, params \\ %{}) do
  model
  |> cast(params, ~w(name username))
  |> validate_required(~w(name username))
  |> unique_constraint(:username)
  |> validate_length(:username, min: 1, max: 20)
end

def registration_changeset(model, params) do
  model

PragTob

iex(13)> user = Repo.get_by(User, name: "Homer")
iex(14)> user.videos
#Ecto.Association.NotLoaded<association :videos is not loaded>
iex(17)> user = Repo.preload(user, :videos)
iex(18)> user.videos
# all the videos

PragTob

def new(conn, _params) do
  changeset = User.new_changeset(%User{})
  render conn, "new.html", changeset: changeset
end

PragTob

with {:ok, record} <- validate_data(params),
     {:ok, record} <- validate_in_other_system(record),
     {:ok, record} <- Repo.insert(record) do
  {:ok, record}
else
  {:error, changeset} -> {:error, changeset}
end

PragTob

config
|> Benchee.init
|> Benchee.system
|> Benchee.benchmark("job", fn -> magic end)
|> Benchee.measure
|> Benchee.statistics
|> Benchee.Formatters.Console.output
|> Benchee.Formatters.HTML.output

PragTob

mp3_byte_size = (byte_size(binary) - 128)
<< _ :: binary-size(mp3_byte_size), id3_tag :: binary >> = binary

<< "TAG",
    title   :: binary-size(30), 
    artist  :: binary-size(30), 
    album   :: binary-size(30), 
    year    :: binary-size(4), 
    comment :: binary-size(30), 
    _rest   :: binary >> = id3_tag

PragTob

defmodule Patterns do
  def greet(%{name: name, age: age}) do
    IO.puts "Hi there #{name}, what's up at #{age}?"
  end
  def greet(%{name: "José Valim"}) do
    IO.puts "Hi José, thanks for elixir! <3"
  end
  def greet(%{name: name}) do
    IO.puts "Hi there #{name}"
  end