What is NSZombie?

ios iphone objective-c nszombie
Moshe picture Moshe · Nov 12, 2010 · Viewed 35.3k times · Source

I've seen suggestions saying to set NSZombieEnabled to true while debugging. What is NSZombie? Is it a framework? A setting?

Answer

Adam Wright picture Adam Wright · Nov 12, 2010

It's a memory debugging aid. Specifically, when you set NSZombieEnabled then whenever an object reaches retain count 0, rather than being deallocated it morphs itself into an NSZombie instance. Whenever such a zombie receives a message, it logs a warning rather than crashing or behaving in an unpredictable way. As such, you can debug subtle over-release/autorelease problems without advanced tools or painstaking needle in haystack searches.

The name is a fairly obvious play on the fact that objects are normally considered "dead" when they reach retain count 0. With this setting, they continue to exist in a strange half-life - neither living, nor quite dead. Much like real zombies, except they eat rather fewer brains.

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