> On Feb 2, 2017, at 3:46 PM, Rex Fenley <r...@remind101.com> wrote: > > My use case is RLMArray and it can't implement RangeReplaceableCollection > though because `init` is unavailable, additionally, there's a lot of parts to > the protocol that would take some time to implement correctly if I could. > They offer a Swift type List that wraps RLMArray and does a bunch of stuff to > implement RangeReplaceableCollection, but they discourage using their Swift > library in mixed Obj-C/Swift projects and certain model objects simply > couldn't use the List type anyway because they're also used in Obj-C and List > is not @objc compliant. > > So this leaves me in situations where when I need to use Array or RLMArray I > have to duplicate my code, not just in one place, but all the way down a > pipeline in order to have my generics work with either > RangeReplaceableCollection or RLMArray. > > If I could abstract the commonalities required by my application, I could > just have a RLMArrayProtocol that has RLMArray's exposed function signatures > and a new protocol Appendable = RangeReplaceableCollection | RLMArrayProtocol > and this will type check all the way through the pipeline. > > tl;dr - if a function signature required by a protocol is marked unavailable > on a class, then disjunction is necessary in order to bridge the two (or > more) types without duplicating code.
You should be able to solve this problem today by creating a custom protocol that you use as a constraint in your generic code and providing conformances for both Array and RLMArray. > > On Thu, Feb 2, 2017 at 1:35 PM, Matthew Johnson <matt...@anandabits.com > <mailto:matt...@anandabits.com>> wrote: >> >> On Feb 2, 2017, at 3:26 PM, Rex Fenley via swift-evolution >> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >> >> Hello, I believe there was some discussion about this quite awhile ago. I >> was wondering if there's any interest in including a protocol 'or' type that >> would be the intersection of two protocols. This could be really useful in >> situations where a framework that the user has no control over implements a >> portion of some often used protocol. Such as specialized collections from an >> Database framework that don't implement RangeReplaceableCollection but have >> a set of methods that are equivalent. The user can then implement a protocol >> that is the intersection of those set of methods and not duplicate code. > > If the specialized collection in the database framework already provides > functionality equivalent to `RangeReplaceableCollection` what you really want > to do is just provide the conformance you’re looking for in an extension: > > extension SpecializedDatabaseCollection: RangeReplaceableCollection { > // if necessary, provide forwarding wrappers where the member names don’t > match up. > } > > But in a case like this the framework itself really should provide this > conformance out of the box. If they didn’t, maybe there is a good reason so > you would want to find out why it wasn’t provided. > > Is there something you’re hoping to do that you can’t solve by simply > extending the framework types? > >> >> Simplified example: >> >> protocol Animal { >> var hasEars: Bool { get } >> func grow() >> } >> >> protocol Plant { >> var isGreen: Bool { get } >> func grow() >> } >> >> protocol LivingThing = Plant | Animal // or a different syntax >> >> LivingThing's is as follows >> { >> func grow() >> } >> >> -- >> Rex Fenley | IOS DEVELOPER >> >> >> Remind.com <https://www.remind.com/> | BLOG <http://blog.remind.com/> | >> FOLLOW US <https://twitter.com/remindhq> | LIKE US >> <https://www.facebook.com/remindhq>_______________________________________________ >> swift-evolution mailing list >> swift-evolution@swift.org <mailto:swift-evolution@swift.org> >> https://lists.swift.org/mailman/listinfo/swift-evolution >> <https://lists.swift.org/mailman/listinfo/swift-evolution> > > > > > -- > Rex Fenley | IOS DEVELOPER > > > Remind.com <https://www.remind.com/> | BLOG <http://blog.remind.com/> | > FOLLOW US <https://twitter.com/remindhq> | LIKE US > <https://www.facebook.com/remindhq>
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