Add fetching support for models

lib/mogli/model.rb

@@ -88,6 +88,12 @@ def self.has_association(name,klass)
       add_creation_method(name,klass)
     end
 
+    def fetch
+      raise ArgumentError.new("You cannot fetch models without a populated id attribute") if id.nil?
+      other = self.class.find(id,client)
+      merge!(other)
+    end
+
     def self.recognize?(data)
       true
     end

spec/model_spec.rb

@@ -93,11 +93,24 @@ class TestModel < Mogli::Model
     model.comments_create 
   end
 
-  it "should emit warnings when properties that don't exist are written to" do
+  it "emits warnings when properties that don't exist are written to" do
     model.should_receive(:warn_about_invalid_property).with("doesnt_exist")
     model.doesnt_exist=1
   end
 
+  describe "Fetching" do
 
+    it "fetches data for a model with an id " do
+      Mogli::Client.should_receive(:get).with("http://graph.facebook.com/1", :query=>{}).and_return({:id=>1,:other_property=>2})
+      model.fetch
+      model.other_property.should == 2
+    end
+
+    it "raises an exception when there is no id" do
+      lambda do
+        TestModel.new.fetch
+      end.should raise_error(ArgumentError)
+    end
+  end
 
 end