How to track at which point a variable gets changed?

Question

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.

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?

Answer 1

Found a solution without hacking the code:

1. Launch debugger with breakpoints enabled

2. Set a breakpoint at some point where the variable in question is in scope

3. Run. When it halts, inspect the debugger and find that variable.

4. Right-click on it and choose "Watch Variable".