On 24 Jul 2017, at 07:04, somu subscribe via swift-users <swift-users@swift.org> wrote:
> - Is there a bug in my code which is being detected in Xcode 9 ? Yes. The problem here is that `doSomething(f1:)` is a mutating function, so it acts like it takes an `inout` reference to `self.helper`. That’s one mutable reference. It then calls `Car.f1()`, which tries to get a non-mutating reference to exactly the same struct. This is outlawed in Swift 4 as part of the memory ownership effort. You can read more about the specific change in SE-0176 “Enforce Exclusive Access to Memory”. <https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md> And the general background to this in the “Ownership Manifesto" <https://github.com/apple/swift/blob/master/docs/OwnershipManifesto.md> > If so could you please explain and suggest an alternate approach / fix ? It’s hard to offer concrete suggestions without knowing more about your high-level goals. One option is for `doSomething(f1:)` to pass the `inout` reference through to `f1`. For example: mutating func doSomething(f1: (inout Helper) -> ()) { f1(&self) } func f1(h: inout Helper) { _ = h.v1 // no crash } but whether that makes sense in your code is for you to decide. Share and Enjoy -- Quinn "The Eskimo!" <http://www.apple.com/developer/> Apple Developer Relations, Developer Technical Support, Core OS/Hardware _______________________________________________ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
