Cache fields

Reset the cache if the relationships or the attributes change

Author: lgebhardt

lib/jsonapi/basic_resource.rb

@@ -455,6 +455,7 @@ def inherited(subclass)
         subclass._warned_missing_route = false
 
         subclass._clear_cached_attribute_options
+        subclass._clear_fields_cache
       end
 
       def rebuild_relationships(relationships)
@@ -530,6 +531,7 @@ def attributes(*attrs)
 
       def attribute(attribute_name, options = {})
         _clear_cached_attribute_options
+        _clear_fields_cache
 
         attr = attribute_name.to_sym
 
@@ -697,7 +699,7 @@ def sortable_field?(key, context = nil)
       end
 
       def fields
-        _relationships.keys | _attributes.keys
+        @_fields_cache ||= _relationships.keys | _attributes.keys
       end
 
       def resources_for(records, context)
@@ -1067,6 +1069,8 @@ def construct_order_options(sort_params)
       end
 
       def _add_relationship(klass, *attrs)
+        _clear_fields_cache
+
         options = attrs.extract_options!
         options[:parent_resource] = self
 
@@ -1115,6 +1119,10 @@ def _clear_cached_attribute_options
         @_cached_attribute_options = {}
       end
 
+      def _clear_fields_cache
+        @_fields_cache = nil
+      end
+
       private
 
       def check_reserved_resource_name(type, name)