Question

我正在尝试更好地了解ARC并使用Apples Documentation

通过第一个例子，我没有得到Apple所说的预期结果; ＆＃34;因为弱引用并没有对它所引用的实例保持强大的保持，所以当弱引用仍然引用它时，该实例可能被释放。因此，当引用它的实例被解除分配时，ARC会自动设置对nil的弱引用。＆＃34;

我在XCode 8.3.2中使用游乐场

import UIKit

class Person {
    let name: String
    init(name: String) { self.name = name }
    var apartment: Apartment?
    deinit { print("\(name) is being deinitialized") }
}

class Apartment {
    let unit: String
    init(unit: String) { self.unit = unit }
    weak var tenant: Person?
    deinit { print("Apartment \(unit) is being deinitialized") }
}


var john: Person?
var unit4A: Apartment?

john = Person(name: "John Appleseed")
unit4A = Apartment(unit: "4A")

john!.apartment = unit4A
unit4A!.tenant = john

john = nil //This prints "John Appleseed is being deinitialized" (as expected)
unit4a?.tenant?.name //This shows "John Appleseed" (expected nil)
unit4a = nil //Prints "Unit4a is being deinitialized" (as expected)

据我所知，这会阻止强大的参考周期，以便两者都可以被取消初始化，但我不明白为什么unit4a会保留对租户的引用？

ARC弱var Swift（不是闭包）

0 个答案: