weak vs strong pointers behaving slightly differently in xcode 5 - ios

Question

i have some code that was working happily in xcode 4.6. since i upgraded to xcode 5 one section was not working. it's not erroring. very oddly the exact same code with no modifications DOES work in the simulators, but does NOT work on devices. if i compile the same coe in xcode 4.6 it DOES work on devices as well as simulators.
it uses tony millions reachability class.
i have tracked down the issue but becasue itworks on simulators in xcode 5, i dont understand.
basically on a button click i check the reachability.
i have a weak pointer to a reachability object, which i setup on the button click - snippet below
#interface settingsViewController ()
#property (weak,nonatomic) Reachability *reachable;
#end
....
//called on click
/ Checks if we have an internet connection or not
- (void)testInternetConnection
{
self.reachable= [Reachability reachabilityWithHostname:#"www.google.com"];
if (self.reachable)
{
NSLog(#"reachability created");
}
else
{
NSLog(#"NO OBJECT");
}
//do more stuff.....
}
basically without changing ANYTHING in the simulators the debug console prints "reachability created" but on ANY device (iPhone/ipad, IOS6/IOS7) the debug console prints "NO OBJECT"
tony milions code to create the object using reachabilityWithHostname is below
#pragma mark - class constructor methods
+(Reachability*)reachabilityWithHostname:(NSString*)hostname
{
SCNetworkReachabilityRef ref = SCNetworkReachabilityCreateWithName(NULL, [hostname UTF8String]);
NSLog(#"init1");
if (ref)
{
NSLog(#"init2");
id reachability = [[self alloc] initWithReachabilityRef:ref];
#if __has_feature(objc_arc)
NSLog(#"init with arc");
return reachability;
#else
NSLog(#"init no arc");
return [reachability autorelease];
#endif
}
NSLog(#"cannot init");
return nil;
}
and on both the simulator and device the debug console prints "init with arc" as expected.
so basically it creates the object OK, but as soon as i test it on the simulator it is valid, but on the device it is null. that bit i dont understand.
BUT if i change the reachability object to be a strong pointer, the simulator continues to work AND the device works as well - in that when i test the reachability object, it is set and the debug console prints "reachability created"
i dont understand how the object can be null as soon as it's created ONLY on the device with a weak pointer... surely
a) the simulator and device should behave the same
b) i have only just created the object the line before - how has it become null on the device if i'm using weak pointer?/
thanks in advance!

Answer 1

The code you posted should never work.
The fact that it does work on simulators is an artifact of the imperfect nature of the simulator, not a reflection that it SHOULD work.
The compiler should be giving you a warning that creating an object and saving it to a weak pointer, it will be released immediately. That's how ARC works.
Use a local strong variable. As soon as the strong variable goes out of scope, it will be up to the caller to decide if it should retain a strong reference to the object.