deprecation_message.ex

# Programming Phoenix Version: P1.0 (April 2016)
# I have the following changeset for my User model:

def changeset(model, params \\ :empty) do
  model
  |> cast(params, ~w(name username), [])
  |> validate_length(:username, min: 1, max: 20)
end

# but I get the following deprecation warning
# when I run the following line in `iex -S mix`

changeset = Rumbl.User.changeset(%Rumbl.User{username: "eric"})

# warning: `Ecto.Changeset.cast/4` is deprecated, please use `cast/3` + `validate_required/3` instead
#     (rumbl) web/models/user.ex:15: Rumbl.User.changeset/2
#     (stdlib) erl_eval.erl:670: :erl_eval.do_apply/6
#     (stdlib) erl_eval.erl:438: :erl_eval.expr/5
#     (elixir) src/elixir.erl:224: :elixir.erl_eval/3
#
# So I changed the changeset to the following:

def changeset(model, params \\ :empty) do
  model
  |> cast(params, ~w(name username))
  |> validate_required([:name, :username])
  |> validate_length(:username, min: 1, max: 20)
end

# But then another deprecation warning is show:
# warning: passing :empty to Ecto.Changeset.cast/3 is deprecated, please pass an empty map or :invalid instead
#     (rumbl) web/models/user.ex:15: Rumbl.User.changeset/2
#     (stdlib) erl_eval.erl:670: :erl_eval.do_apply/6
#     (stdlib) erl_eval.erl:438: :erl_eval.expr/5
#     (elixir) src/elixir.erl:224: :elixir.erl_eval/3

# running the following works fine however:
changeset = Rumbl.User.changeset(%Rumbl.User{username: "eric"}, %{})