ARC会在对象没有强引用时自动释放对象，但是如果在类中声明了deinit方法，即使没有其他引用对象的变量或常量，该对象也不会立即释放，而是等到deinit方法执行完毕后才会释放。例如：

class Person { var name: String init(name: String) { self.name = name print(name + " is being initialized") } deinit { print(name + " is being deinitialized") } }

var person1: Person? = Person(name: "Tom") var person2: Person? = Person(name: "Jerry")

person1 = nil person2 = nil

输出： Tom is being initialized Jerry is being initialized Tom is being deinitialized Jerry is being deinitialized

可以看到，当person1和person2的引用都置为nil时，Person对象并没有立即被释放，而是在deinit方法执行完毕后才被释放。