til/rails/format-amount-as-currency.md

Format Amount As Currency

I was checking various sums of dollar amounts in a Rails console recently. However, they are returned as BigDecimal and display in exponential notation.

PaymentLink.joins(:payment).during(:last_month).sum("payments.amount")
# => 0.12345678e6

When it comes to dollar amounts I find that notation to be hard to parse at a glance. With Rails' help I can quickly format them as currency with the number_to_currency method from ActionView's NumberHelper.

include ActionView::Helpers::NumberHelper
number_to_currency(PaymentLink.joins(:payment).during(:last_month).sum("payments.amount"))
# => "$123,456.78"

There are some options that can be passed to number_to_currency to further customize it, like precision:

number_to_currency(PaymentLink.joins(:payment).during(:last_month).sum("payments.amount"), precision: 0)
# => "$123,457"