Introduced StockTaking. TODO: Dry up the stockit/stock_takings/deliveries controllers/views!

app/models/stock_article.rb

@@ -30,6 +30,8 @@ class StockArticle < Article
 
   named_scope :available, :conditions => "quantity > 0"
 
+  before_destroy :check_quantity
+
   # Update the quantity of items in stock
   def update_quantity!
     update_attribute :quantity, stock_changes.collect(&:quantity).sum
@@ -46,4 +48,10 @@ class StockArticle < Article
     end
     available
   end
+
+  protected
+
+  def check_quantity
+    raise "#{name} kann nicht gelöscht werden. Der Lagerbestand ist nicht null." unless quantity == 0
+  end
 end