I was surprised that the key-paths subscript setter does access the properties getter. This made this example crash:
struct DelayedMutable<Value> {
private var _value: Value? = nil
var isInitialized: Bool {
return _value != nil
}
var value: Value {
get {
guard let value = _value else {
fatalError("property accessed before being initialized")
}
return value
}
set {
_value = newValue
}
}
/// "Reset" the delegate so it can be initialized again.
mutating func reset() {
_value = nil
}
}
private var _value = DelayedMutable<Int>()
var value: Int {
get { return _value[keyPath: \.value] }
set { _value[keyPath: \.value] = newValue }
}
value = 42
What am I missing or why does the setter needs to access the getter of the destination property before setting it?
