Add Format Amount As Currency as a Rails TIL

README.md

@@ -10,7 +10,7 @@ working across different projects via [VisualMode](https://www.visualmode.dev/).
 
 For a steady stream of TILs, [sign up for my newsletter](https://visualmode.kit.com/newsletter).
 
-_1880 TILs and counting..._
+_1881 TILs and counting..._
 
 See some of the other learning resources I work on:
 
@@ -1221,6 +1221,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Find Records With Multiple Associated Records](rails/find-records-with-multiple-associated-records.md)
 - [Flipper Discards Actors When Feature Fully Enabled](rails/flipper-discards-actors-when-feature-fully-enabled.md)
 - [Force All Users To Sign Out](rails/force-all-users-to-sign-out.md)
+- [Format Amount As Currency](rails/format-amount-as-currency.md)
 - [Format DateTime With Builtin Formats](rails/format-datetime-with-builtin-formats.md)
 - [Format Specific html.erb Template Files](rails/format-specific-html-erb-template-files.md)
 - [Generate A Model](rails/generate-a-model.md)

rails/format-amount-as-currency.md

@@ -0,0 +1,28 @@
+# 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.
+
+```ruby
+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`](https://api.rubyonrails.org/classes/ActiveSupport/NumberHelper.html#method-i-number_to_currency)
+method from `ActionView`'s `NumberHelper`.
+
+```ruby
+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`:
+
+```ruby
+number_to_currency(PaymentLink.joins(:payment).during(:last_month).sum("payments.amount"), precision: 0)
+# => "$123,457"
+```