Check out https://developer.apple.com/videos/wwdc/2015/?id=401 (time 14:30).
Three new lang features: nullability, lightweight generics, kindof types. On Tue, Jun 9, 2015 at 11:37 AM, Jens Alfke <[email protected]> wrote: > The new generics support in Objective-C (starting in Xcode 7) is > interesting, although there’s no real documentation that I can find, just a > one-paragraph mention in the Foundation release notes. But if you look at > NSArray.h or NSDictionary.h in the OS X 10.11 or iOS 9 SDK, you can see > lots of examples of their use. > > (There’s also a somewhat related new keyword __kindof, also described in > the release notes, that gives you un-typechecked down-casting. So an RHS of > type “__kindof NSView*” can be assigned to a LHS of type MyViewClass* > without a type-cast. Nice.) > > I’m guessing that the primary reason generics were added was to make the > Cocoa APIs more Swift-friendly, so the Swift APIs don’t just use > [AnyObject] and [AnyObject:AnyValue] everywhere. > > They’ll be useful for Obj-C programming too though, of course. I tried > parameterizing the NSArray and NSDictionary types that appear in some APIs > in my code, and everything rebuilt without errors. Which is nice in that it > didn’t break everything and require massive replacing; but on the other > hand it shows that generics are pretty loosely type-checked. It seems that > you can freely assign between, say, NSArray<NSString*>* and a regular > NSArray* without any warnings or errors. In fact you can use the generic > form in a method’s declaration in a class interface, but leave the old form > in the @implementation, without any warnings. > > For backward compatibility in my APIs I’m doing stuff like this: > > #if __has_feature(objc_generics) > typedef NSDictionary<NSString*, id> CBLJSONDict; > #else > typedef NSDictionary CBLJSONDict; > #endif > > and then replacing “NSDictionary” with “CBLJSONDict” where appropriate. > > —Jens > > _______________________________________________ > Do not post admin requests to the list. They will be ignored. > Objc-language mailing list ([email protected]) > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/objc-language/shazron%40gmail.com > > This email sent to [email protected] >
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