我在玩耍时发现:

// Array of weak references of a protocol OK so long as protocol marked @objc
@objc protocol P { // Note @objc
    var i: Int { get }
}
class CP: P {
    var i: Int = 0
}
let weakPs: [WeakReference<P>] = [WeakReference(value: cP)] // Note typed as `[WeakReference<P>]`
print("P: \(weakPs[0].value!.i)") // 0

有效:)

令人讨厌的是，您必须使用@objc，因此不能使用纯粹的Swift解决方案，但是由于我在iOS上使用，这对我来说不是问题.

It is annoying that you have to use @objc and therefore not a pure Swift solution, but since I am on iOS not a problem for me.