1 files changed, 77 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/attribute_set.rb b/activerecord/lib/active_record/attribute_set.rb
new file mode 100644
index 0000000000..66fcaf6945
--- /dev/null
+++ b/activerecord/lib/active_record/attribute_set.rb
@@ -0,0 +1,77 @@
+require 'active_record/attribute_set/builder'
+
+module ActiveRecord
+  class AttributeSet # :nodoc:
+    def initialize(attributes)
+      @attributes = attributes
+    end
+
+    def [](name)
+      attributes[name] || Attribute.null(name)
+    end
+
+    def values_before_type_cast
+      attributes.transform_values(&:value_before_type_cast)
+    end
+
+    def to_hash
+      initialized_attributes.transform_values(&:value)
+    end
+    alias_method :to_h, :to_hash
+
+    def key?(name)
+      attributes.key?(name) && self[name].initialized?
+    end
+
+    def keys
+      attributes.initialized_keys
+    end
+
+    def fetch_value(name)
+      self[name].value { |n| yield n if block_given? }
+    end
+
+    def write_from_database(name, value)
+      attributes[name] = self[name].with_value_from_database(value)
+    end
+
+    def write_from_user(name, value)
+      attributes[name] = self[name].with_value_from_user(value)
+    end
+
+    def write_cast_value(name, value)
+      attributes[name] = self[name].with_cast_value(value)
+    end
+
+    def freeze
+      @attributes.freeze
+      super
+    end
+
+    def initialize_dup(_)
+      @attributes = attributes.dup
+      super
+    end
+
+    def initialize_clone(_)
+      @attributes = attributes.clone
+      super
+    end
+
+    def reset(key)
+      if key?(key)
+        write_from_database(key, nil)
+      end
+    end
+
+    protected
+
+    attr_reader :attributes
+
+    private
+
+    def initialized_attributes
+      attributes.select { |_, attr| attr.initialized? }
+    end
+  end
+end