what is difference between alloc and allocWithZone:?

Question

From forum discussion , seem like that the big difference is performance factor, allocWithZone: will alloc memory from particular memory area, which reduce cost of swapping.

Answer 1

Even if the Apple's Documentation indicates that allocWithZone:

exists for historical reasons; memory zones are no longer used by Objective-C. You should not override this method.

and

Zones are ignored on iOS and 64-bit runtime on OS X. You should not use zones in current development.

in reality I overridden it in an Objective-C class (in a full Objective-C project) and the method is called when I do [[Mylass alloc] init] even if the build is running on an iPhone 6s.

But I think it's better to follow the documentation and override alloc method instead of this one because alloc can certainly do the same job.