I have very newbie question. How can i check that object of model is valid with new params BEFORE updating it? I want transform that: def update @obj = SomeModel.find( params[:id] ) if @obj.update_attributes( params[:obj] ) # That have been updated else # Ups, errors! end end To something like that: def update @obj = SomeModel.find( params[:id] ) if @obj.valid_with_new_params( params[:obj] ) @obj.