Why retain a static variable?

objective-c memory-management retain static-variables
ma11hew28 picture ma11hew28 · Jun 11, 2011 · Viewed 7.2k times · Source

Isn't it unnecessary to retain a static variable since it stays around for the duration of the program, no matter if you release it?

See this code: https://github.com/magicalpanda/MagicalRecord/blob/master/Source/Categories/NSManagedObjectContext+MagicalRecord.m#L24-29

Answer

Jonathan Grynspan picture Jonathan Grynspan · Jun 11, 2011

I'm assuming you mean a static object pointer, such as static NSString *foobar;.

Such variables indeed have a lifetime as long as the application, but the variables we're talking about are pointers only. In Objective-C, objects are always dynamically allocated, and so we always address them with a pointer to their type, but the underlying data for an object is still present out in the dynamically allocated wild blue yonder.

You must still retain the object because, while the pointer to the object will never go out of scope, the object itself can be deallocated just like any other object, and so your pointer will end up pointing to garbage, or worse, another unrelated object.

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