Guards and Control Flow

Guard: when #

If #

if (condition, do: this, else: that)

if(condition, [do: this, else: that])

if(condition, [{:do, this}, {:else, that}])

if true do
  this
else
  that
end

if(true, do: (this), else: (that))

if true do
  this
  that
end

if(true, do: (
  this
  that
))

falsey = false or nil

truthy = everything that is not false or nil

Case #

case condition do
  x when x in [false, nil] -> cases...
  _ -> cases..
end

Case is most commonly used for the insert actions

# liveview
def save_post(socket, :new, post_params) do
  case Blog create_post(post_params) do
    {:ok, post } -> 
      notify_parent({:saved, post})
      {:no_reply, socket |> put_flash(:info, "ok")} |> push_patch(to: socket.assigns.patch}
    {:ok, %Ecto.changeset = changeset } -> 
      {:no_reply, assign_form(socket, changeset)}

# phoenix
def create(conn, %{"email" => email_params}) do
  case Emails.create_email(email_params) do  

Cond #

cond do
  age >= 10 -> IO.puts "A"
  age <= 10 -> IO.puts "B"
  true -> IO.puts "Z" # fallback
end  

with #

Assuming a chain of conditions:

m = %{a: 1, c: 3}

a =
  with {:ok, number} <- Map.fetch(m, :a),
    true <- is_even(number) do
      IO.puts "#{number} divided by 2 is #{div(number, 2)}"
      :even
  else
    :error ->
      IO.puts("We don't have this item in map")
      :error
    _ ->
      IO.puts("It is odd")
      :odd
  end


with {:ok, variable} <- Module.action(changeset),
     {:ok, token, full_claims} <- Guardian.encode_and_sign(user, :token, claims) do
  important_stuff(token, full_claims)
end