Add Convert JSON Field To Hash With Indifferent Access as a Rails TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1680 TILs and counting..._
+_1681 TILs and counting..._
 
 See some of the other learning resources I work on:
 
@@ -1051,6 +1051,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Comparing DateTimes Down To Second Precision](rails/comparing-datetimes-down-to-second-precision.md)
 - [Conditional Class Selectors in Haml](rails/conditional-class-selectors-in-haml.md)
 - [Convert A Symbol To A Constant](rails/convert-a-symbol-to-a-constant.md)
+- [Convert JSON Field To Hash With Indifferent Access](rails/convert-json-field-to-hash-with-indifferent-access.md)
 - [Count The Number Of Records By Attribute](rails/count-the-number-of-records-by-attribute.md)
 - [Create A Custom Named References Column](rails/create-a-custom-named-references-column.md)
 - [Create A Join Table With The Migration DSL](rails/create-a-join-table-with-the-migration-dsl.md)

rails/convert-json-field-to-hash-with-indifferent-access.md

@@ -0,0 +1,36 @@
+# Convert JSON Field To Hash With Indifferent Access
+
+Let's say we have an `Event` model whose backing table includes a `JSONB` (or
+`JSON`) field called `details`.
+
+When we access `details` in a Rails context, digging into that nested data we
+have to use string keys throughout. However, we may have existing related code
+that is dealing with this shape of data using symbol keys. This might put us in
+a position where we have to rework a bunch of existing code or do defensive
+coding like `details[:user] || details["user"]`.
+
+To avoid that, we can instead have the `Event` model override `details`
+converting that underlying data to `HashWithIndifferentAccess` before returning
+it.
+
+```ruby
+class Event < ApplicationRecord
+  def details
+    data = super
+    return data if data.nil?
+    
+    case data
+    when Array
+      data.map { |item| item.is_a?(Hash) ? item.with_indifferent_access : item }
+    when Hash
+      data.with_indifferent_access
+    else
+      data
+    end
+  end
+end
+```
+
+With this in place, anywhere in the codebase where we access `details` on an
+instance of `Event` we will be able to use string or symbol keys
+interchangeably.