Add the #reset_attributes method

lib/virtus/instance_methods.rb

@@ -176,6 +176,34 @@ def reset_attribute(attribute_name)
       self
     end
 
+    # Reset all attributes to their defaults
+    #
+    # @return [self]
+    #
+    # @api public
+    #
+    # @example
+    #
+    #   class User
+    #     include Virtus
+    #
+    #     attribute :age,  Integer, default: 21
+    #     attribute :name, String, default: 'Jane'
+    #   end
+    #
+    #   user = User.new(:name => 'John', :age => 28)
+    #   user.name # => John
+    #   user.age  # => 28
+    #   user.reset_attributes
+    #   user.name # => Jane
+    #   user.age  # => 21
+    #
+    # @api public
+    def reset_attributes
+      attributes.keys.each { |attribute_name| reset_attribute(attribute_name) }
+      self
+    end
+
     # Set default attributes
     #
     # @return [self]

spec/integration/default_values_spec.rb

@@ -15,7 +15,7 @@ class Page
         include Virtus
 
         attribute :title,        String
-        attribute :slug,         String,  :default => lambda { |post, attribute| post.title.downcase.gsub(' ', '-') }, :lazy => true
+        attribute :slug,         String,  :default => lambda { |post, attribute| post.title && post.title.downcase.gsub(' ', '-') }, :lazy => true
         attribute :view_count,   Integer, :default => 0
         attribute :published,    Boolean, :default => false, :accessor => :private
         attribute :editor_title, String,  :default => :default_editor_title, :lazy => true
@@ -59,6 +59,16 @@ def default_editor_title
     end.to change { subject.view_count }.to(0)
   end
 
+  specify 'you can reset all attributes to their defaults' do
+    subject.view_count = 10
+    subject.editor_title = "UNPUBLISHED: Top Secret"
+
+    subject.reset_attributes
+
+    expect(subject.view_count).to eq(0)
+    expect(subject.editor_title).to eq("UNPUBLISHED: ")
+  end
+
   context 'a ValueObject' do
     it 'does not duplicate the ValueObject' do
       page1 = Examples::Page.new