title: How to track at which point a variable gets changed?
body: <p>I have a BOOL instance variable which -for some reason- some time later always reads NO even if I set it to YES (Yes, I am not so stupid to write or read the wrong variable, trust me). I spent an hour searching my whole project for any possibilities where that variable might be set to NO but can't find it.</p>
  
  <p>Is there a way to trace changes of it's value, i.e. to let the debugger halt at exactly the position where the variable is about to be modified?</p>