Don't fill in timestamp fields if they are disabled for a table

lib/dynamoid/fields.rb

@@ -21,6 +21,9 @@ module Fields
       class_attribute :range_key
 
       self.attributes = {}
+
+      # Timestamp fields could be disabled later in `table` method call.
+      # So let's declare them here and remove them later if it will be necessary
       field :created_at, :datetime if Dynamoid::Config.timestamps
       field :updated_at, :datetime if Dynamoid::Config.timestamps
 
@@ -83,9 +86,13 @@ def table(options)
         end
 
         if options[:timestamps] && !Dynamoid::Config.timestamps
+          # Timestamp fields weren't declared in `included` hook because they
+          # are disabled globaly
           field :created_at, :datetime
           field :updated_at, :datetime
         elsif options[:timestamps] == false && Dynamoid::Config.timestamps
+          # Timestamp fields were declared in `included` hook but they are
+          # disabled for a table
           remove_field :created_at
           remove_field :updated_at
         end
@@ -107,6 +114,10 @@ def remove_field(field)
         end
       end
 
+      def timestamps_enabled?
+        options[:timestamps] || (options[:timestamps].nil? && Dynamoid::Config.timestamps)
+      end
+
       private
 
       def generated_methods
@@ -174,14 +185,14 @@ def read_attribute_before_type_cast(name)
     #
     # @since 0.2.0
     def set_created_at
-      self.created_at ||= DateTime.now.in_time_zone(Time.zone) if Dynamoid::Config.timestamps
+      self.created_at ||= DateTime.now.in_time_zone(Time.zone) if self.class.timestamps_enabled?
     end
 
     # Automatically called during the save callback to set the updated_at time.
     #
     # @since 0.2.0
     def set_updated_at
-      if Dynamoid::Config.timestamps && !updated_at_changed?
+      if self.class.timestamps_enabled? && !updated_at_changed?
         self.updated_at = DateTime.now.in_time_zone(Time.zone)
       end
     end

lib/dynamoid/persistence/import.rb

@@ -32,7 +32,7 @@ def call
       def build_model(attributes)
         attrs = attributes.symbolize_keys
 
-        if Dynamoid::Config.timestamps
+        if @model_class.timestamps_enabled?
           time_now = DateTime.now.in_time_zone(Time.zone)
           attrs[:created_at] ||= time_now
           attrs[:updated_at] ||= time_now