Ecto change password w/ confirmation.

model.ex

defmodule User do
  use Ecto.Model
  
  schema "users" do
    field :email, :string
    field :hashed_password, :string
    field :password, :string, virtual: true
    field :password_confirmation, virtual: true
    
    timestamps
  end
  
  before_save :hash_password
  
  @required [:email, :password, :password_confirmation]
  @optional []
  def changeset(user, params) do
    params
    |> cast(user, @required, @optional)
    |> validate_format(:email, ~r/@/)
    |> validate_password_confirmation
  end
  
  defp validate_password_confirmation(%{changes: changes} = changeset) do
    case changes[:password_confirmation] do
      changes[:password] -> changeset
      _ -> add_error(changeset, :password_confirmation, "must match password")
    end
  end
  
  defp hash_password(changeset) do
    #hash things
  end
end

route.ex

defmodule API.User do
  import Plug.Conn
  
  post "/" do
    change = User.changeset(%User{}, params(conn))
    if change.valid? do
      send_resp(conn, 200, JSON.Encode(Repo.update(change)))
    else
      send_resp(conn, 422, JSON.Encode(change.errors))
    end
  end
end