Do you think if there will be any evolution proposal to address this limitation? Or it’s an inherent tradeoff that is unlikely to be changed?
> On 19 Jul 2017, at 8:49 AM, Jordan Rose <jordan_r...@apple.com> wrote: > > > >> On Jul 18, 2017, at 10:33, Vladimir.S via swift-users <swift-users@swift.org >> <mailto:swift-users@swift.org>> wrote: >> >> On 17.07.2017 4:51, Glen Huang via swift-users wrote: >>> Thanks for the code sample and link, but if I’m not wrong, this pattern >>> doesn’t allow heterogeneous items. >> >> Support the question. Trying to understand if we can have something like >> [AnyHashable] for our custom protocol(with associated type) or AnyHashable >> has a very special support from compiler and we can use only [Any] or such >> kind of wrapper: >> >> struct AnyMyProtocol { >> let actualInstance: Any >> init<T: MyProtocol>(_ instance: T) { actualInstance = instance} >> } >> >> let instances: [AnyMyProtocol] = [AnyMyProtocol(...), AnyMyProtocol(...)] >> >> if let some = instances[0].actualInstance as? >> SpecificImplementationOfMyProtocol { >> // use 'some' as SpecificImplementationMyProtocol instance >> // seems like no way to refer to just MyProtocol >> } > > AnyHashable is special, sorry. You'll have to use this sort of indirect > unwrapping instead. You can write a little convenience method for it though, > if you want: > > extension AnyMyProtocol { > func get<T: MyProtocol>(as: T.Type) -> T? { > return self.actualInstance as? T > } > } > > if let some = instances[0].get(as: SpecificImplementationOfMyProtocol.self) { > // use 'some' here > } > > Jordan
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