Everyone stay calm, these zombies don’t mean any harm!
In Cocoa, objects released from memory will be kept around as “Zombies” if you enable a flag named
An attempt to access a freed object is a common bug in Cocoa Programming that leads to a crash.
NSZombieEnabled helps you save a lot of time debugging your message to Zombie (released object).
When you try to call a de-allocated object with the
NSZombieEnabled flag set, you will be notified by recording stops rather than simply crashing your application.
To enable this power move:
- Select “Edit Scheme…” from the “Product” menu (or, press Cmd+Shift+<).
- Select the “Run” on the left side of the scheme editor.
- Select the “Arguments” tab in right side page.
- Add a new item (press ‘+’) in Environment Variable and call it
- Set its value to
Any more calls to the zombie after this will ask the system to stop the program by running a breakpoint, and you can take a look at the chain of calls that the zombie sends in the backtrack.
Learn more about it here.