Do inheritance in a clearer way

There's no need for code to be repeated in every subclass. The only thing that really needs to change is what the unused field is.

The difference between this and what was there before is that the unused field is stripped from both local and remote whereas in the case of the Load Balancer, it won't be in the local. This doesn't matter though, as there is a test for whether it's present before attemptint to remove it.

lib/vcloud/edge_gateway/configuration_differ.rb

@@ -14,11 +14,21 @@ def diff
         end
 
         def stripped_local_config
-          @local
+          return @stripped_local unless @stripped_local.nil?
+          return nil if @local.nil?
+          @stripped_local = strip_unused_field_from_config(@local)
+          @stripped_local
         end
 
         def stripped_remote_config
-          @remote
+          return @stripped_remote unless @stripped_remote.nil?
+          return nil if @remote.nil?
+          @stripped_remote = strip_unused_field_from_config(@remote)
+          @stripped_remote
+        end
+
+        def strip_unused_field_from_config(config)
+          config
         end
 
     end

lib/vcloud/edge_gateway/firewall_configuration_differ.rb

@@ -2,23 +2,7 @@ module Vcloud
   module EdgeGateway
     class FirewallConfigurationDiffer < ConfigurationDiffer
 
-        def stripped_local_config
-          return @stripped_local unless @stripped_local.nil?
-          return nil if @local.nil?
-          @stripped_local = strip_id_param_from_firewall_rules(@local)
-          @stripped_local
-        end
-
-        def stripped_remote_config
-          return @stripped_remote unless @stripped_remote.nil?
-          return nil if @remote.nil?
-          @stripped_remote = strip_id_param_from_firewall_rules(@remote)
-          @stripped_remote
-        end
-
-        private
-
-        def strip_id_param_from_firewall_rules(config)
+        def strip_unused_field_from_config(config)
           deep_cloned_config = Marshal.load( Marshal.dump(config) )
           if deep_cloned_config.key?(:FirewallRule)
             deep_cloned_config[:FirewallRule].each do |firewall_rule|

lib/vcloud/edge_gateway/load_balancer_configuration_differ.rb

@@ -2,16 +2,7 @@ module Vcloud
   module EdgeGateway
     class LoadBalancerConfigurationDiffer < ConfigurationDiffer
 
-        def stripped_remote_config
-          return @stripped_remote unless @stripped_remote.nil?
-          return nil if @remote.nil?
-          @stripped_remote = strip_operational_field_from_config(@remote)
-          @stripped_remote
-        end
-
-        private
-
-        def strip_operational_field_from_config(config)
+        def strip_unused_field_from_config(config)
           deep_cloned_remote_config = Marshal.load( Marshal.dump(config) )
           if deep_cloned_remote_config.key?(:Pool)
             deep_cloned_remote_config[:Pool].each do |pool_entry|

lib/vcloud/edge_gateway/nat_configuration_differ.rb

@@ -2,23 +2,7 @@ module Vcloud
   module EdgeGateway
     class NatConfigurationDiffer < ConfigurationDiffer
 
-        def stripped_local_config
-          return @stripped_local unless @stripped_local.nil?
-          return nil if @local.nil?
-          @stripped_local = strip_id_param_from_nat_rules(@local)
-          @stripped_local
-        end
-
-        def stripped_remote_config
-          return @stripped_remote unless @stripped_remote.nil?
-          return nil if @remote.nil?
-          @stripped_remote = strip_id_param_from_nat_rules(@remote)
-          @stripped_remote
-        end
-
-        private
-
-        def strip_id_param_from_nat_rules(config)
+        def strip_unused_field_from_config(config)
           deep_cloned_config = Marshal.load( Marshal.dump(config) )
           if deep_cloned_config.key?(:NatRule)
             deep_cloned_config[:NatRule].each do |nat_rule|