ios - Retain Cycle Even when using Weak/Strong ARC Semantics -

`i admit not expert on arc , retain cycles though through research , great articles (like this), believe basics.

however, stumped. have property defined follows.

@property (nonatomic,retain) foo *foo; 

inside init, following.

if(self = [super init]) {      _foo = [[foo alloc] initwithdelegate:self];      // async rest     __weak typeof(self) weakself = self;     dispatch_async(dispatch_get_global_queue(dispatch_queue_priority_default,                                              (unsigned long)null), ^(void) {          __strong typeof(weakself) strongself = weakself;          if (strongself.foo != nil) {                         [strongself.foo runtests];         }     }); } return self; } 

and here dealloc

- (void)dealloc {      _foo = nil; } 

if dispatch_aync block commented out, see foo dealloc called after foo set nil. block commented in, foo's delloc not called.

i've got retain cycle correct? idea how?

no, not have retain cycle (now known "strong reference cycle" in arc). have code that, if foo existed time strongself defined, foo retained until dispatched code finishes.

the potential strong reference cycle here delegate passed foo. if delegate defined strong property of foo class, have strong reference cycle. if it's defined weak property, have no strong reference cycle.