Memory Leak

[moxian1993]

这段代码会导致内存泄漏：

let timer = Timer(timeInterval: duration, target: self, selector: #selector(UIView.toastTimerDidFinish(_:)), userInfo: toast, repeats: false)

分析原因如下：

1. self -> toast： self.addSubview(toast)
2. toast -> timer： objc_setAssociatedObject(toast, &ToastKeys.timer, timer, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
3. timer -> self(target): Timer(timeInterval: duration, target: self, selector: #selector(UIView.toastTimerDidFinish(_:)), userInfo: toast, repeats: false)

可行的解决方案: 使用 weakProxy

// 将原先代码改成：
let weakProxy = WeakProxy(self)
let timer = Timer(timeInterval: duration, target: weakProxy, selector: #selector(UIView.toastTimerDidFinish(_:)), userInfo: toast, repeats: false)

// WeakProxy 实现
class WeakProxy: NSObject {
    weak var target: NSObjectProtocol?
    static func proxyWithTarget(target:NSObjectProtocol) -> WeakProxy {
        return WeakProxy.init(target: target)
    }

    init(target:NSObjectProtocol) {
        self.target = target
        super.init()
    }
    
    override func forwardingTarget(for aSelector: Selector!) -> Any? {
        return target
    }
    
    override func responds(to aSelector: Selector!) -> Bool {
        return target?.responds(to: aSelector) ?? false || super.responds(to: aSelector)
    }
}