Construct UnknownAttribute error message uniformly

Author: andrykonchin

lib/dynamoid/errors.rb

@@ -86,7 +86,16 @@ class InvalidQuery < Error; end
 
     class UnsupportedKeyType < Error; end
 
-    class UnknownAttribute < Error; end
+    class UnknownAttribute < Error
+      attr_reader :model_class, :attribute_name
+
+      def initialize(model_class, attribute_name)
+        super("Attribute #{attribute_name} does not exist in #{model_class}")
+
+        @model_class = model_class
+        @attribute_name = attribute_name
+      end
+    end
 
     class SubclassNotFound < Error; end
 

lib/dynamoid/fields.rb

@@ -291,7 +291,7 @@ def write_attribute(name, value)
       old_value = read_attribute(name)
 
       unless attribute_is_present_on_model?(name)
-        raise Dynamoid::Errors::UnknownAttribute, "Attribute #{name} is not part of the model"
+        raise Dynamoid::Errors::UnknownAttribute.new(self.class, name)
       end
 
       if association = @associations[name]

lib/dynamoid/persistence/update_validations.rb

@@ -7,9 +7,9 @@ module UpdateValidations
       def self.validate_attributes_exist(model_class, attributes)
         model_attributes = model_class.attributes.keys
 
-        attributes.each_key do |attr_name|
-          unless model_attributes.include?(attr_name)
-            raise Dynamoid::Errors::UnknownAttribute, "Attribute #{attr_name} does not exist in #{model_class}"
+        attributes.each_key do |name|
+          unless model_attributes.include?(name)
+            raise Dynamoid::Errors::UnknownAttribute.new(model_class, name)
           end
         end
       end