ARC 中的递归块和保留循环

自动引用计数（ARC）是一种在iOS和MacOS开发中用于管理内存的技术。在ARC中，使用递归块和保留循环可以更好地处理内存管理问题。本文将介绍ARC中的递归块和保留循环的概念，并提供一些案例代码来说明它们的用法。

swift
class Person {
    let name: String
    var child: Person?
    init(name: String) {
        self.name = name
    }
    deinit {
        print("\(name) is being deinitialized")
    }
}
var john: Person?
var jane: Person?
john = Person(name: "John")
jane = Person(name: "Jane")
john?.child = jane
jane?.child = john
john = nil
jane = nil

swift
class Person {
    let name: String
    var car: Car?
    init(name: String) {
        self.name = name
    }
    deinit {
        print("\(name) is being deinitialized")
    }
}
class Car {
    let model: String
    weak var owner: Person?
    init(model: String) {
        self.model = model
    }
    deinit {
        print("Car model \(model) is being deinitialized")
    }
}
var john: Person?
var car: Car?
john = Person(name: "John")
car = Car(model: "BMW")
john?.car = car
car?.owner = john
john = nil
car = nil