Swift--15内存管理

//Swift的内存管理

class Human {

deinit {

print("对象即将释放")

}

}

var xiaoMing: Human? = Human()

var xiaoWang: Human? = xiaoMing

if xiaoMing === xiaoWang {

print("同一对象")

} else {

print("不同对象")

}

xiaoMing = nil

xiaoWang = nil

//弱引用(weak)

class Person {

var name: String

init (name: String) {

self.name = name

}

deinit {

print("(name) 被释放")

}

var apartment: Apartment?

}

class Apartment {

var number: Int

init(number: Int) {

self.number = number

}

deinit {

print("#(number)公寓被释放")

}

//公寓可能没有主人，建议使用weak，这样可以避免强引用

//当引用的实例销毁时，ARC会将该引用设置为nil

weak var tenant: Person?

}

//定义约翰和73号公寓

var john: Person?

var num73: Apartment?

john = Person(name: "John")

num73 = Apartment(number: 73)

#if true

//此时会造成循环强引用，两对象都无法释放

john?.apartment = num73

num73?.tenant = john

#endif

john = nil

//当引用的实例销毁时，ARC会将该引用设置为nil

print(num73?.tenant as Any) //nil

num73 = nil

//无主引用(unowned)

class Customer {

var name: String

var card: CreditCard?

init(name: String) {

self.name = name

}

deinit {

print("Customer: (name) 被释放")

}

}

class CreditCard {

var number: Int

//若该引用始终有值，建议使用unowned，可以避免强引用

unowned let customer: Customer

init(number: Int,customer: Customer) {

self.number = number

self.customer = customer

}

deinit {

print("Card: #(number) 被释放")

}

}

var tom: Customer?

tom = Customer(name: "Tom")

tom?.card = CreditCard(number: 12345678,customer: tom!)

tom = nil

//闭包引起的强引用

class Student {

var name: String

init (name: String) {

self.name = name

}

deinit {

print("Student (name) 被释放")

}

lazy var fullName: ()->String = {

//闭包中使用self，会造成强引用(即使多次使用self也只是引用一次)

[unowned self] in

return "王氏.(self.name)"

}

}

var stu: Student? = Student(name: "Lucy")

var fullName = stu?.fullName

//stu = nil

print(fullName!())

（编辑：李大同）

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