I am trying to get something very similar to the example in the WWDC 2017 Foundation talk working for KVO observing. The only differences that I see that are different from that talk are, I had to call super.init(), and I had to make the "kvo" token implicitly unwrapped.
The following is used in a playground:
struct Node {
let title: String
let leaf: Bool
var children: [String: Node] = [:]
}
let t = Node(title:"hello", leaf:false, children:[:])
let k1 = \Node.leaf
let k2 = \Node.children
t[keyPath: k1] // returns "false" works
t[keyPath: k2] // returns "[:]" works
@objcMembers class MyController : NSObject {
dynamic var tr: Node
var kvo : NSKeyValueObservation!
init(t: Node) {
tr = t
super.init()
kvo = observe(\.tr) { object, change in
print("\(object) \(change)")
}
}
}
let x = MyController(t: t)
x.tr = Node(title:"f", leaf:false, children:[:])
x
This error:
> fatal error: Could not extract a String from KeyPath
> Swift.ReferenceWritableKeyPath<__lldb_expr_3.MyController,
> __lldb_expr_3.Node>: file /Library/Caches/com.apple.xbs/Sources/swiftlang/swiftlang-900.0.45.6/src/swift/stdlib/public/SDK/Foundation/NSObject.swift,
> line 85
Also, see this error:
> error: Execution was interrupted, reason: EXC_BAD_INSTRUCTION
> (code=EXC_I386_INVOP, subcode=0x0). The process has been left at the
> point where it was interrupted, use "thread return -x" to return to
> the state before expression evaluation.
Is anyone else able to get something like this working, or is this a bug I need to report?
