Add default values for elements

README.md

@@ -69,7 +69,9 @@ class AtomEntry
   # The :as argument makes this available through entry.author instead of .name
   element :name, as: :author
   element "feedburner:origLink", as: :url
-  element :summary
+  # The :default argument specify value for element
+  # if it will not be found in XML
+  element :summary, class: Integer, default: 0
   element :content, class: AtomContent
   element :published
   ancestor :ancestor
@@ -104,6 +106,7 @@ feed.feed_url # The URL of the blog feed
 feed.entries.first.title # Title of the first entry
 feed.entries.first.author # The author of the first entry
 feed.entries.first.url # Permalink on the blog for this entry
+feed.entries.first.summary # Returns 0 as value if not found
 feed.entries.first.ancestor # The Atom ancestor
 feed.entries.first.content # Instance of AtomContent
 feed.entries.first.content.text # Entry content text

lib/sax-machine/config/sax_element.rb

@@ -1,7 +1,7 @@
 module SAXMachine
   class SAXConfig
     class ElementConfig
-      attr_reader :name, :setter, :data_class, :collection
+      attr_reader :name, :as, :setter, :data_class, :collection, :default
 
       def initialize(name, options)
         @name = name.to_s
@@ -15,6 +15,7 @@ def initialize(name, options)
 
         @as = options[:as]
         @collection = options[:collection]
+        @default = options[:default]
 
         @setter = if @collection
           "add_#{options[:as]}"

lib/sax-machine/sax_document.rb

@@ -33,6 +33,17 @@ def initialize(attributes = {})
       attributes.each do |name, value|
         send("#{name}=", value)
       end
+
+      self.class.sax_config.top_level_elements.each do |name, configs|
+        configs.each do |config|
+          next unless config.default
+
+          current_value = send("#{config.as.to_s}")
+          next unless current_value.nil?
+
+          send("#{config.setter}", config.default)
+        end
+      end
     end
   end
 

spec/sax-machine/sax_document_spec.rb

@@ -153,6 +153,18 @@ def title=(val)
         end
       end
 
+      describe "the default attribute" do
+        it "is available" do
+          @klass = Class.new do
+            include SAXMachine
+            element :number, default: ""
+          end
+
+          document = @klass.parse("<wrong>data</wrong>")
+          expect(document.number).to eq("")
+        end
+      end
+
       describe "the required attribute" do
         it "is available" do
           @klass = Class.new do