Fixed an issue using the association_name= method to assign a new obj…

…ect updated existing pointers to the proxy, rather than generating a new one

lib/mongo_mapper/plugins/associations.rb

@@ -33,17 +33,23 @@ def create_association(type, name, options, &extension)
             association = Associations::Base.new(type, name, options, &extension)
             associations[association.name] = association
 
-            define_method("#{association.name}=") do |value|
-              get_proxy(association).replace(value)
-              value
-            end
-
             if association.one? || association.belongs_to?
               define_method(association.name) do
                 proxy = get_proxy(association)
                 proxy.nil? ? nil : proxy
               end
 
+              define_method("#{association.name}=") do |value|
+                proxy = get_proxy(association)
+
+                if (proxy.nil? || proxy.target != value)
+                  proxy = build_proxy(association)
+                end
+
+                proxy.replace(value)
+                value
+              end
+
               define_method("#{association.name}?") do
                 get_proxy(association).present?
               end
@@ -66,6 +72,11 @@ def create_association(type, name, options, &extension)
                 get_proxy(association)
               end
 
+              define_method("#{association.name}=") do |value|
+                get_proxy(association).replace(value)
+                value
+              end
+
             end
 
             if association.options[:dependent] && association.many? && !association.embeddable?
@@ -95,11 +106,17 @@ def embedded_associations
             association
           end
         end
-
+
+        def build_proxy(association)
+          proxy = association.proxy_class.new(self, association)
+          self.instance_variable_set(association.ivar, proxy)
+
+          proxy
+        end
+
         def get_proxy(association)
           unless proxy = self.instance_variable_get(association.ivar)
-            proxy = association.proxy_class.new(self, association)
-            self.instance_variable_set(association.ivar, proxy)
+            proxy = build_proxy(association)
           end
           proxy
         end

test/functional/associations/test_belongs_to_proxy.rb

@@ -36,7 +36,27 @@ def setup
     comment.post.should == post
     comment.post.nil?.should be_false
   end
+
+  should "generate a new proxy when replacing the association" do 
+    post1 = @post_class.create(:name => 'post1')
+    post2 = @post_class.create(:name => 'post2')
+
+    comment = @comment_class.new(:name => 'Foo!', :post => post1)
+    comment.save.should be_true
+
 
+    comment = comment.reload
+    comment.post.should == post1
+    comment.post.nil?.should be_false
+
+    original_post = comment.post
+    original_post.name.should == 'post1'
+
+    comment.post = post2
+    comment.post.name.should == 'post2'
+    original_post.name.should == 'post1'
+  end
+
   should "unset the association" do
     post = @post_class.new(:name => 'mongomapper')
     comment = @comment_class.new(:name => 'Foo!', :post => post)

test/functional/associations/test_one_proxy.rb

@@ -47,8 +47,28 @@ def setup
         post.author = new_author
         post.author.should == new_author
       end
-    end
+
+      should "generate a new proxy instead of modifying the existing one" do
+        @post_class.one :author, :class => @author_class
+
+        post = @post_class.new
+        author = @author_class.new(:name => 'Frank')
+        post.author = author
+        post.reload
 
+        post.author.should == author
+        post.author.nil?.should be_false
+
+        original_author = post.author
+        original_author.name.should == 'Frank'
+        new_author = @author_class.new(:name => 'Emily')
+        post.author = new_author
+        post.author.should == new_author
+
+        original_author.name.should == 'Frank'
+      end
+    end
+
     context "with a Hash" do
       should "convert to an object of the class and work" do
         @post_class.one :author, :class => @author_class