I used mix phx.gen.json
to generate a simple User resource. Among the files it generated, two of them are
user_controller.ex
defmodule MyapiWeb.UserController do
use MyapiWeb, :controller
alias Myapi.Accounts
alias Myapi.Accounts.User
action_fallback MyapiWeb.FallbackController
def index(conn, _params) do
users = Accounts.list_users()
render(conn, "index.json", users: users)
end
def create(conn, %{"user" => user_params}) do
with {:ok, %User{} = user} <- Accounts.create_user(user_params) do
conn
|> put_status(:created)
|> put_resp_header("location", Routes.user_path(conn, :show, user))
|> render("show.json", user: user)
end
end
def show(conn, %{"id" => id}) do
user = Accounts.get_user!(id)
render(conn, "show.json", user: user)
end
def update(conn, %{"id" => id, "user" => user_params}) do
user = Accounts.get_user!(id)
with {:ok, %User{} = user} <- Accounts.update_user(user, user_params) do
render(conn, "show.json", user: user)
end
end
def delete(conn, %{"id" => id}) do
user = Accounts.get_user!(id)
with {:ok, %User{}} <- Accounts.delete_user(user) do
send_resp(conn, :no_content, "")
end
end
end
and fallback_controller.ex
defmodule MyapiWeb.FallbackController do
@moduledoc """
Translates controller action results into valid `Plug.Conn` responses.
See `Phoenix.Controller.action_fallback/1` for more details.
"""
use MyapiWeb, :controller
def call(conn, {:error, %Ecto.Changeset{} = changeset}) do
IO.inspect(changeset)
conn
|> put_status(:unprocessable_entity)
|> put_view(MyapiWeb.ChangesetView)
|> render("error.json", changeset: changeset)
end
def call(conn, {:error, :not_found}) do
conn
|> put_status(:not_found)
|> put_view(MyapiWeb.ErrorView)
|> render(:"404")
end
end
My question is regarding the def call(conn, {:error, :not_found})
function in fallback_controller.ex
. When it is called ?
-
When a User is created or updated which is not valid,
def call(conn, {:error, %Ecto.Changeset{} = changeset})
is called. I know how fallback withwith
works. -
When
show
ordelete
function inuser_controller.ex
is called with the wrong user_id, Ecto.NoResultsError is converted to 404 response.
So, what is the point of def call(conn, {:error, :not_found})
function in fallback_controller.ex
? When is it called ?