title: Unrecognized selector sent to Core Data causes app crash
body: <p>I have a iPad app, using XCode 4.5, Storyboards, iOS 6 and MagicalRecord.  This code is causing the error, and I don't see why.  Both <code>aApptStart</code> and <code>selectedStartDate</code> are defined as DateTime.  So, what is causing this?</p>
  
  <p>Here is the offending code:</p>
  
  <pre><code>- (IBAction)saveAppointment:(UIButton *)sender {
  
      NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread];
      AppointmentInfo *newAppointment = [AppointmentInfo createEntity];  //  create the entity
  
      NSLog(@"Selected start Date (save): %@", [self formatSelectedDate: selectedStartDate]); 
  
      newAppointment.aApptStart = selectedStartDate;  //  &lt;------  causing the error
      newAppointment.aApptEnd= selectedEndDate;
      newAppointment.aTech = selectedTech;
  
      [localContext MR_saveNestedContexts];
  }
  </code></pre>
  
  <p>Here is the error I'm getting:</p>
  
  <blockquote>
    <p>Terminating app due to uncaught exception
    'NSInvalidArgumentException', reason: '-[NSManagedObject
    setAApptStart:]: unrecognized selector sent to instance 0xee85dd0'</p>
  </blockquote>