Reduce complexity reported by codeclimate

lib/puffy/formatters/pf.rb

@@ -116,13 +116,21 @@ def emit_address(host, if_unspecified = 'any')
         def emit_rdr_to(rule)
           return unless rule.rdr?
 
-          keyword = Puffy::Formatters::Base.loopback_addresses.include?(rule.rdr_to_host) ? 'divert-to' : 'rdr-to'
+          keyword = rdr_to_keyword(rule)
           destination = rule.rdr_to_host || loopback_address(rule.af)
           raise 'Unspecified address family' if destination.nil?
 
           emit_endpoint_specification(keyword, destination, rule.rdr_to_port)
         end
 
+        def rdr_to_keyword(rule)
+          if Puffy::Formatters::Base.loopback_addresses.include?(rule.rdr_to_host)
+            'divert-to'
+          else
+            'rdr-to'
+          end
+        end
+
         def emit_nat_to(rule)
           "nat-to #{emit_address(rule.nat_to)}" if rule.nat_to
         end

lib/puffy/rule.rb

@@ -64,8 +64,7 @@ class Rule
     def initialize(options = {})
       send_options(options)
 
-      @af = detect_af unless af
-
+      self.af ||= detect_af
       self.proto ||= from_proto_hint || to_proto_hint
 
       raise "unsupported action `#{options[:action]}'" unless valid_action?