raise an exception when replacing frozen association

CHANGELOG

@@ -1,3 +1,5 @@
+* raise an exception when trying to replace frozen association
+
 *0.1.0* (July 14th, 2008)
 
 * initial release

lib/association_freezer/belongs_to_freezer.rb

@@ -18,10 +18,14 @@ def fetch(*args)
       frozen || nonfrozen(*args)
     end
 
+    def frozen?
+      frozen_data
+    end
+
     private
 
     def frozen
-      @frozen ||= load_frozen if frozen_data
+      @frozen ||= load_frozen if frozen?
     end
 
     def load_frozen
@@ -40,10 +44,6 @@ def frozen_data
       @owner.read_attribute("frozen_#{name}")
     end
 
-    def attribute_name
-      "frozen_#{name}"
-    end
-
     def target_class
       @reflection.klass
     end

lib/association_freezer/method_generator.rb

@@ -29,6 +29,16 @@ def generate
         send(freezer).fetch(*args)
       end
       model_class.alias_method_chain reflection.name, :frozen_check
+
+      generate_method "#{reflection.name}_with_frozen_check=" do |*args|
+        if send(freezer).frozen?
+          # TODO make this a custom exception
+          raise "Unable to set #{reflection.name} because association is frozen." 
+        else
+          send("#{reflection.name}_without_frozen_check=", *args)
+        end
+      end
+      model_class.alias_method_chain "#{reflection.name}=", :frozen_check
     end
 
     private

spec/freezer_spec.rb

@@ -78,6 +78,15 @@
         @order.unfreeze_ship_method
         @order.ship_method.price.should == 8
       end
+
+      it "should raise an exception when attempting to save associated model" do
+        lambda { @order.ship_method.save }.should raise_error(Exception)
+        lambda { @order.ship_method.save! }.should raise_error(Exception)
+      end
+
+      it "should raise an exception when attempting to replace association" do
+        lambda { @order.ship_method = ShipMethod.new }.should raise_error(Exception)
+      end
     end
   end
 end