Add Rounding Numbers With Precision as a rails til

README.md

@@ -9,7 +9,7 @@ and pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://tinyletter.com/jbranchaud).
 
-_872 TILs and counting..._
+_873 TILs and counting..._
 
 ---
 
@@ -539,6 +539,7 @@ _872 TILs and counting..._
 - [Remove The Default Value On A Column](rails/remove-the-default-value-on-a-column.md)
 - [Rescue From](rails/rescue-from.md)
 - [Retrieve An Object If It Exists](rails/retrieve-an-object-if-it-exists.md)
+- [Rounding Numbers With Precision](rails/rounding-numbers-with-precision.md)
 - [Secure Passwords With Rails And Bcrypt](rails/secure-passwords-with-rails-and-bcrypt.md)
 - [Select A Select By Selector](rails/select-a-select-by-selector.md)
 - [Select Value For SQL Counts](rails/select-value-for-sql-counts.md)

rails/rounding-numbers-with-precision.md

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+# Rounding Numbers With Precision
+
+Ruby's `Float#round` method gets the job done, but doesn't offer much
+configurability. If you'd like to finely control how a rounded number will
+display, `ActiveSupport::NumberHelper` offers
+[`number_to_rounded`](https://api.rubyonrails.org/classes/ActiveSupport/NumberHelper.html#method-i-number_to_rounded).
+
+When a precision is specified, it will apply to the fraction digits:
+
+```ruby
+> ActiveSupport::NumberHelper.number_to_rounded(1.0, precision: 2)
+=> "1.00"
+```
+
+Unless you include `significant: true` in which case precision will refer to
+the number of signficant digits:
+
+```ruby
+> ActiveSupport::NumberHelper.number_to_rounded(1.0, precision: 2, significant: true)
+=> "1.0"
+```
+
+Because this is for display purposes, the return value is a string. You can
+further specify that insignificant zeros are stripped from the result:
+
+```ruby
+> ActiveSupport::NumberHelper.number_to_rounded(1.0, precision: 2, significant: true, strip_insignificant_zeros: true)
+=> "1"
+```
+
+And for completeness, here is an example of a number being rounded up:
+
+```ruby
+> ActiveSupport::NumberHelper.number_to_rounded(1.29, precision: 2, significant: true)
+=> "1.3"
+```
+
+[source](https://api.rubyonrails.org/classes/ActiveSupport/NumberHelper.html#method-i-number_to_rounded)