Prefer object/nil over `true`/`false`

This is the project guideline and the reasons are:

* That follows standard Ruby semantics.
* Allows the implementation to avoid artificial code like !! or something ? true : false
* You do not need to rely on the exact type of 3rd party code. For
example, if your method returns str.end_with?('foo') you do not need to
make sure end_with? returns a singleton. Your predicate just propagates
predicate semantics up regardless of what end_with? returns.

activesupport/lib/active_support/message_verifier.rb

@@ -35,8 +35,8 @@ def initialize(secret, options = {})
     end
 
     def valid_message?(signed_message)
-      return false if signed_message.blank?
-      
+      return if signed_message.blank?
+
       data, digest = signed_message.split("--")
       data.present? && digest.present? && ActiveSupport::SecurityUtils.secure_compare(digest, generate_digest(data))
     end
@@ -47,14 +47,12 @@ def verified(signed_message)
           data = signed_message.split("--")[0]
           @serializer.load(decode(data))
         rescue ArgumentError => argument_error
-          return false if argument_error.message =~ %r{invalid base64}
+          return if argument_error.message =~ %r{invalid base64}
           raise
         end
-      else
-        false
       end
     end
-    
+
     def verify(signed_message)
       verified(signed_message) || raise(InvalidSignature)
     end