斯威夫特 3 &iOS 10 错误内存泄漏错误

问题描述

在 Xcode 8 中与 iOS 10 & 一起使用时似乎存在(错误的)内存泄漏错误斯威夫特 3.

There seems to be a (false) memory leak bug in Xcode 8 when using with iOS 10 & Swift 3.

以下代码报告了 Instruments 和 Xcode 8 内存调试器中的内存泄漏:

The following code reports a memory leak in Instruments and the Xcode 8 memory debugger:

class SomeClass: NSObject {
    var view: SomeView!

    deinit {
        print("SomeClass deinit")
    }
}

class SomeView: UIView {
    weak var reference: SomeClass?

    deinit {
        print("SomeView deinit")
    }
}

class ViewController: UIViewController {
    var someProperty: SomeClass?

    override func viewDidLoad() {
        super.viewDidLoad()

        let c = SomeClass()
        let v = SomeView()
        c.view = v
        v.reference = c

        someProperty = c
    }
}

推荐答案

我尝试了不同的变体来确认它确实是一个错误，我的发现是:

I've tried different variations to confirm it's indeed a bug and my findings are:

1. 当您没有将示例代码中的 c 分配给 someProperty 时，两个实例都将在各自的 deinit 中打印字符串.真正的强引用循环不会取消.
2. 当 SomeClass 不继承自 NSObject 时，不会发生此错误.
3. 使用 Swift 2.2 时，不会发生这种情况.
4. 使用 iOS 9- 时，不会发生这种情况.
5. 一旦 someProperty 在代码中的某处设置为 nil，两个实例都被 deinit ed.Xcode 8 内存调试器确认没有内存泄漏.然而，在 Instruments 中，这种变化并没有反映出来——这是理所当然的，因为真正的内存泄漏可能不会得到解决.

1. When you don't assign c in the sample code to someProperty, both instances will print the string in their respective deinits. A true strong reference cycle won't deinit.
2. When SomeClass doesn't inherit from NSObject, this bug doesn't happen.
3. When using Swift 2.2, this doesn't happen.
4. When using iOS 9-, this doesn't happen.
5. Once someProperty is set to nil somewhere in the code, both instances are deinited. Xcode 8 memory debugger confirms there are no memory leaks. However in Instruments, this change isn't reflected--rightfully so, since a real memory leak probably won't be resolved.

仅供参考，这不会仅在将其分配给 UIViewController 的属性时发生.我最初是在单例对象中发现这种行为的.

FYI, this doesn't happen only when it's assigned to a property of UIViewController. I originally found out about this behavior in a singleton object.

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