延迟初始化和保持循环 [英] Lazy initialisation and retain cycle

问题描述

在使用惰性初始化器时，是否有可能存在保留周期?

在博客文章和许多其他地方[无主的自己]被看见

class Person {变量名:字符串懒惰 var 个性化Greeting:字符串 = {[无主的自己]在return "你好，(self.name)！"}()初始化(名称:字符串){self.name = 姓名}}

我试过了

class Person {变量名:字符串懒惰 var 个性化Greeting:字符串 = {//[无主的自己]在return "你好，(self.name)！"}()初始化(名称:字符串){打印(人初始化")self.name = 姓名}取消初始化{打印(人deinit")}}

就这么用了

//...让人 = 人(姓名:姓名")打印(person.personalizedGreeting)//..

并发现person deinit"已被记录.

所以似乎没有保留周期.据我所知，当一个块捕获 self 并且这个块被 self 强烈保留时，存在一个保留循环.这种情况看起来类似于保留循环，但实际上并非如此.

解决方案

我试过这个 [...]

lazy var personalGreeting: String = { return self.name }()

<块引用>

似乎没有保留周期

正确.

原因是立即应用的闭包 {}() 被认为是 @noescape.它不保留捕获的self.

供参考:Joe Groff 的推文.

While using lazy initialisers, is there a chance of having retain cycles?

In a blog post and many other places [unowned self] is seen

class Person {

    var name: String

    lazy var personalizedGreeting: String = {
        [unowned self] in
        return "Hello, (self.name)!"
        }()

    init(name: String) {
        self.name = name
    }
}

I tried this

class Person {

    var name: String

    lazy var personalizedGreeting: String = {
        //[unowned self] in
        return "Hello, (self.name)!"
        }()

    init(name: String) {
        print("person init")
        self.name = name
    }

    deinit {
        print("person deinit")
    }
}

Used it like this

//...
let person = Person(name: "name")
print(person.personalizedGreeting)
//..

And found that "person deinit" was logged.

So it seems there are no retain cycles. As per my knowledge when a block captures self and when this block is strongly retained by self, there is a retain cycle. This case seems similar to a retain cycle but actually it is not.

解决方案

I tried this [...]

lazy var personalizedGreeting: String = { return self.name }()

it seems there are no retain cycles

Correct.

The reason is that the immediately applied closure {}() is considered @noescape. It does not retain the captured self.

For reference: Joe Groff's tweet.

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