swift - Swift 4 Timer崩溃并带有NSException

我一直在寻找一种在Swift 4中使用Timer的方法，并查看了this文章。我在xcode中测试了我的代码，当计时器第一次计时(在这种情况下为10秒)时，应用程序崩溃了，尽管构建成功，但还是出现了错误。

2017-11-20 19:54:42.781502-0700 Rock Prodigy[3022:554505] -[_SwiftValue   tick]: unrecognized selector sent to instance 0x608000051520
2017-11-20 19:54:42.791278-0700 Rock Prodigy[3022:554505] ***  Terminating app due to uncaught exception 'NSInvalidArgumentException',   reason: '-[_SwiftValue tick]: unrecognized selector sent to instance  0x608000051520'
*** First throw call stack:
(
0   CoreFoundation                      0x000000010360d1ab __exceptionPreprocess + 171
1   libobjc.A.dylib                     0x0000000102ca2f41 objc_exception_throw + 48
2   CoreFoundation                      0x000000010368da34 -[NSObject(NSObject) doesNotRecognizeSelector:] + 132
3   CoreFoundation                      0x00000001035900a8 ___forwarding___ + 1432
4   CoreFoundation                      0x000000010358fa88 _CF_forwarding_prep_0 + 120
5   Foundation                          0x000000010270e1ee __NSFireTimer + 83
6   CoreFoundation                      0x000000010359d2a4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20
7   CoreFoundation                      0x000000010359cf62 __CFRunLoopDoTimer + 1026
8   CoreFoundation                      0x000000010359cb1a __CFRunLoopDoTimers + 266
9   CoreFoundation                      0x0000000103594534 __CFRunLoopRun + 2308
10  CoreFoundation                      0x00000001035939b9 CFRunLoopRunSpecific + 409
11  GraphicsServices                    0x00000001090e29c6 GSEventRunModal + 62
12  UIKit                               0x0000000103a885e8 UIApplicationMain + 159
13  Rock Prodigy                        0x000000010238b637 main + 55
14  libdyld.dylib                       0x0000000107aa1d81 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)

这是我的快速4代码

import UIKit

class GeneralFitness: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    var timer: Timer! = Timer.scheduledTimer(timeInterval: 10, target: self, selector: #selector(tick), userInfo: nil, repeats: true)

    @objc func tick() {
        print("tick")
    }


}

如果您有任何问题，请告诉我。

最佳答案

作为Andrea said，您应该在viewDidLoad中实例化计时器。也是the documentation says:

并且不要忘记在viewDidDisappear中禁用此计时器。您无法在invalidate中对其进行deinit编码，因为重复计时器会牢牢引用其目标，并且只要计时器正在运行，您的deinit都不会被调用。并且，如果您将其以viewDidDisappear删除，则可能要在viewDidAppear中创建计时器。

因此，结果如下:

class ViewController: UIViewController {

    weak var timer: Timer?

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        timer = Timer.scheduledTimer(timeInterval: 10, target: self, selector: #selector(tick(_:)), userInfo: nil, repeats: true)
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)

        timer?.invalidate()
    }

    @objc func tick(_ timer: Timer) {
        print("tick")
    }

}

或者，您可以使用带有[weak self]模式的基于块的再现，并且计时器不会对 View Controller 保持强大的引用，在这种情况下，您可以使用deinit:

class ViewController: UIViewController {

    var timer: Timer?

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        timer = Timer.scheduledTimer(withTimeInterval: 10, repeats: true) { [weak self] timer in  // the `[weak self] reference is only needed if you reference `self` in the closure
            print("tick")
        }
    }

    deinit {
        timer?.invalidate()
    }

}

Deinit

swift - Swift 4 Timer崩溃并带有NSException