elixir with syntax
def call(conn, _options) do
with user_id when not is_nil(user_id) <- get_session(conn, :user_id),
user when not is_nil(user) <- Repo.get(User, user_id)
do
assign(conn, :current_user, user)
else
_ ->
conn
|> Controller.put_flash(:error, "You have to sign in to access this page.")
|> Controller.redirect(to: "/sign_in_links/new")
|> halt
end
end