Re: Warning from Xcode build
Re: Warning from Xcode build
- Subject: Re: Warning from Xcode build
- From: Quincey Morris <email@hidden>
- Date: Sun, 14 Aug 2016 21:31:17 -0700
- Feedback-id: 167118m:167118agrif8a:167118s4Y5oYa_0x:SMTPCORP
On Aug 14, 2016, at 20:08 , Ben Kennedy <email@hidden> 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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