Programming Phoenix 1.4

Managing Registration Changesets

You’ve already seen a changeset for creating a new user, the one that handles the name and username. Let’s review that now:

authentication/rumbl/lib/rumbl/accounts/user.ex

def changeset(user, attrs) do
  user
  |> cast(attrs, [:name, :username])
  |> validate_required([:name, :username])
  |> validate_length(:username, min: 1, max: 20)
end

The Ecto.Changeset.cast function converts a raw map of user input to a changeset, accepting only the :name and :username keys. Then, we fire a validation limiting the length of valid usernames to twenty characters. A failing validation places errors in the changeset so we can display them to the user.

As you might expect, you’ll use one changeset per ...