Works like a charm, thanks. > On 7 Oct 2017, at 2:56 PM, Slava Pestov <spes...@apple.com> wrote: > > You can try upcasting the value to NSObject first, and then performing a > conditional downcast to Controller1 and Controller2. At this point the type > checker will not have enough information to decide that the cast always > fails, and should no longer emit a warning. > > Slava > >> On Oct 6, 2017, at 11:55 PM, Glen Huang <hey...@gmail.com >> <mailto:hey...@gmail.com>> wrote: >> >> Done, https://bugs.swift.org/browse/SR-6083 >> <https://bugs.swift.org/browse/SR-6083> >> >> In the mean time, is there any workaround? Or it’s not possible to check the >> concrete type without this issue being fixed? >> >>> On 7 Oct 2017, at 2:44 PM, Slava Pestov <spes...@apple.com >>> <mailto:spes...@apple.com>> wrote: >>> >>> Oh I see. I think the problem is that with Objective-C generics, you can >>> always cast from Foo<A> to Foo<B>, because the type parameters do not >>> really exist. Swift’s type checking logic for casts assumes Swift generic >>> semantics, where in general Foo<A> and Foo<B> are unrelated types. >>> >>> Do you mind filing a bug? >>> >>> Slava >>> >>>> On Oct 6, 2017, at 11:40 PM, Glen Huang <hey...@gmail.com >>>> <mailto:hey...@gmail.com>> wrote: >>>> >>>> NSFetchedResultsController is the class from Core Data: >>>> >>>> https://developer.apple.com/documentation/coredata/nsfetchedresultscontroller >>>> >>>> <https://developer.apple.com/documentation/coredata/nsfetchedresultscontroller> >>>> >>>>> On 7 Oct 2017, at 2:38 PM, Slava Pestov <spes...@apple.com >>>>> <mailto:spes...@apple.com>> wrote: >>>>> >>>>> Can you post a self-contained example, including the declaration of >>>>> NSFetchedResultsController? >>>>> >>>>> Slava >>>>> >>>>>> On Oct 6, 2017, at 11:28 PM, Glen Huang via swift-users >>>>>> <swift-users@swift.org <mailto:swift-users@swift.org>> wrote: >>>>>> >>>>>> Hi, >>>>>> >>>>>> I defined some concrete classes inheriting from a generic class like >>>>>> this: >>>>>> >>>>>> class Controller1: NSFetchedResultsController<NSManagedObject> {} >>>>>> class Controller2: NSFetchedResultsController<NSManagedObject> {} >>>>>> >>>>>> And I assign them a shared delegate, and in the delegate method: >>>>>> >>>>>> func controllerWillChangeContent(_ controller: >>>>>> NSFetchedResultsController<NSFetchRequestResult>) >>>>>> >>>>>> I want to test the concrete type of controller, doing things differently >>>>>> for Controller1 and Controller2. >>>>>> >>>>>> But doing the following gives me a warning: Cast from >>>>>> 'NSFetchedResultsController<NSFetchRequestResult>' to unrelated type >>>>>> 'Controller1’ always fails >>>>>> >>>>>> switch controller { >>>>>> case is Controller1: >>>>>> // ... >>>>>> default: >>>>>> break >>>>>> } >>>>>> >>>>>> I wonder what’s the correct way to check the concrete type? >>>>>> >>>>>> Regards, >>>>>> Glen >>>>>> _______________________________________________ >>>>>> swift-users mailing list >>>>>> swift-users@swift.org <mailto:swift-users@swift.org> >>>>>> https://lists.swift.org/mailman/listinfo/swift-users >>>>> >>>> >>> >> >
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