title: Using KVC operator e.g., @unionOfSets/@sum in IB's Value Binding Model Key Path
body: <p>I am not sure if this can be done -- it looks like it should be a straightforward thing but I keep getting "the entity Sale is not key value coding-compliant for the key "@sum"."</p>
  
  <p>I using "@unionsOfSets.departments.@sale.amount" for the Table column value binding. 
  I am doing it right, or what is the right way to do this?</p>
  
  <p><img src="https://lh4.ggpht.com/_xpwq_Sv0p98/Sw42pO41olI/AAAAAAAAAow/8LX3Ap-31og/s800/Screen%20shot%202009-11-26%20at%203.13.03%20PM.png" alt="Screenshot"></p>