While i definitely see the potential for generics as an effective tool to prevent runtime type-mismatch errors, i feel like the loose-type checking kind of defeats the purpose... Hopefully xcode will implement the functionality to at least flag it as a warning in their static analyzer
Best, BK > On Jun 9, 2015, at 2:37 PM, 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/bkimstunnaboss%40gmail.com > > This email sent to [email protected]
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