An Ecto.Type storing a currency as its ISO 4217 code in a text column.

A currency is identified by its code — :USD, :EUR, :JPY — and that code is all that needs storing; the currency's name, symbol and digits are reference data looked up from the code, not per-row data. So the column is ordinary text holding the code, needing no migration beyond the column itself.

Values cast and load as the validated code atom, so a stored currency can carry a foreign key, a unique index, or a CHECK constraint like any other text, and an unknown code is rejected on the way in.

Schema

# in a migration
add :currency, :string

# in a schema
field :currency, Localize.Currency.Ecto.Type

Casting

cast/1 accepts a code as an atom (:USD) or string ("USD", in any case), or a Localize.Currency.t/0 struct, and validates it against Localize.Currency.validate_currency/1. An unknown code returns an error rather than being stored.