AshMoney Usage Rules

AshMoney provides AshMoney.Types.Money (aliased as :money if configured), backed by ex_money.

Type Usage

attribute :balance, :money
attribute :balance, AshMoney.Types.Money

storage_type — :money_with_currency (default, requires ex_money_sql for Postgres) or :map
min / max — decimal bounds on the amount
ex_money_opts — keyword list passed to Money.new/3

attribute :charge, :money do
  constraints min: Decimal.new("0"), max: Decimal.new("1000")
end

Money.new(:USD, "100.00")
Money.new!("EUR", Decimal.new("50"))

In expressions (composite type):

composite_type(%{currency: "USD", amount: Decimal.new("0")}, :money)

Supported in Ash expressions (runtime and Postgres when the extension is installed):

+ — add two Money values
- — subtract two Money values; unary negation
* — multiply Money by a decimal
<, <=, >, >= — compare two Money values, or Money against a decimal

Currency mismatches raise errors. All arithmetic requires matching currencies.

With AshMoney.AshPostgresExtension installed, money operations push down to SQL. Access composite fields in expressions via:

filter expr(balance[:currency_code] == "USD")

Aggregates work naturally:

sum :total, :line_items, :amount