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.
In practice, almost get no chance to use allocWithZone: , anyone can give simple example to illustrate which case to use allocWithZone: ?
Thanks,
When one object creates another, it’s sometimes a good idea to make sure they’re both allocated from the same region of memory. The zone method (declared in the NSObject protocol) can be used for this purpose; it returns the zone where the receiver is located.
This suggests to me that your ivars, and any objects your classes "create" themselves could make use of +allocWithZone: in this way, to make the instances they create in the same zone.
-(id)init {
if (self = [super init]) {
someIvar = [[SomeOtherClass allocWithZone:[self zone]] init];
}
return self;
}