Add Convert A Symbol To A Constant as a rails til

rails/convert-a-symbol-to-a-constant.md

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+# Convert A Symbol To A Constant
+
+If you have a symbol and need to convert it to a constant, perhaps because
+of some metaprogramming induced by a polymorphic solution, then you may
+start off on an approach like the following. In fact, I've seen a number of
+StackOverflow solutions like this.
+
+```ruby
+:module.to_s.capitalize.constantize
+#=> Module
+```
+
+That is great for one-word constant names, but what about multi-word
+constants like `OpenStruct`. This approach will not work for the symbol
+`:open_struct`. We need a more general solution.
+
+The key is to ditch `#capitalize and instead use another ActiveSupport
+method, `#classify`.
+
+```ruby
+:open_struct.to_s.classify.constantize
+#=> OpenStruct
+```