Add Reference Hash Key With Safe Navigation as a Ruby TIL

ruby/reference-hash-key-with-safe-navigation.md

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+# Reference Hash Key With Safe Navigation
+
+Let's say we have a variable that we expect to be a hash, but could also be
+`nil`. We want to try to grab a value from that hash by referencing a specific
+key. Because it could be `nil`, we cannot simply do:
+
+```ruby
+stuff[:key]
+```
+
+As that could result in `NoMethodError: undefined method '[]' for nil
+(NoMethodError)`.
+
+We should use the _safe navigation_ operator (`&`) to avoid raising that error.
+However, we should pay attention to a necessary syntax shift from the short-hand
+`[:key]` to the long-hand `[](:key)`.
+
+```ruby
+stuff&.[](:key)
+```
+
+The meaning of this syntax is that we are calling the `#[]` method and we pass
+it a single argument `:key` wrapped in parentheses.
+
+Another approach would be to use `#dig` which can feel more ergonomic than the
+above syntax switch.
+
+```ruby
+stuff&.dig(:key)
+```