On Aug 14, 2016, at 20:08 , Ben Kennedy <b...@zygoat.ca> wrote: > > Are you sure that's still the case? While I'm admittedly running 10.12 beta > on this machine as I type, I've nonetheless launched Xcode 7.3.1 and created > a test project using the 10.11 SDK. > > In NSApplication.h, NSApp and the delegate property are declared as follows: > >> APPKIT_EXTERN __kindof NSApplication * __null_unspecified NSApp; >> … >> @property (nullable, assign) id<NSApplicationDelegate> delegate; > > When I attempt to assign a delegate after deleting the implementing class's > conformance to NSApplicationDelegate (such that it simply descends from > NSObject), these two semantically-equivalent calls yield different errors > messages: > >> NSApp.delegate = self; >> // Assigning to 'id<NSApplicationDelegate> _Nullable' from incompatible tyoe >> 'AppDelegate *const __strong >> >> [NSApp setDelegate:self]; >> // Sending 'AppDelegate *const __strong' to parameter of incompatible type >> 'id<NSFileManagerDelegate> _Nullable'
You’re correct, the SDK had been changed in 10.11, which I hadn’t noticed. However, in the second form, the receiver is (I would say) *clearly* exhibiting the old behavior**. This may or may not be by intention. In several places I found by searching the __kindof is described as being somewhat “like" ‘id’. For example, in the Xcode 7 release notes: > "Objects declared as __kindof types behave like a mix of id and a specific > object type: They specify an upper bound (for example, must be UIView or a > subclass thereof) but allow implicit downcasting to any subtype of that upper > bound.” I guess this should at least be reported as a bug. ** Indeed, it might be exhibiting the old behavior in the first case, too, with the fact that it chose a NSApplication method being a random accident.
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