title: Update record using Core Data in iOS
body: <p>I can't seem to find an example of how to update an existing row of data using Core Data on iOS. In terms of SQL, I'm looking to do something along the lines of:
  UPDATE device SET attr1='blah', attr2='blah' WHERE deviceid='1';</p>
  
  <p>I know I can do something like this:
  [device setValue:@"blah" forKey:@"attr1"];</p>
  
  <p>However, how can I do that only WHERE the deviceid='1'?</p>
  
  <p>Any help is appreciated.</p>