objective-c - Swift 中的强引用和弱引用

Question

在 Objective C 中，您可以将属性定义为具有强引用或弱引用，如下所示:

@property(strong)...
@property(weak)...

这是如何快速完成的？

Answer 1

直接来自Swift Language guide :

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

class Apartment {
    let number: Int
    init(number: Int) { self.number = number }
    weak var tenant: Person?
    deinit { println("Apartment #\(number) is being deinitialized") }
}

属性默认是强的。但是查看“Apartment”类的租户属性，它被声明为弱。你也可以使用 unowned 关键字，它从 Objective-C 转换为 unsafe_unretained

https://itunes.apple.com/tr/book/swift-programming-language/id881256329?mt=11