title: Mac OS change value of bound core data control
body: <p>I'm just getting started with Core Data.  I have an XCode 8 Swift 3 project with a form with an Array Controller and several bound controls.  The form works perfectly saving and recalling data from Core Data.</p>
  
  <p>I want to put a button on the form that will set values in a couple of the bound text boxes.  I can set the stringValue property of the text boxes and it does change the displayed data, but it does not save the data.  When I move to another record and come back I see the old value.</p>
  
  <p>How do I set the new value so it will be updated in the Core Data store?</p>