Swift：“无法识别的选择器发送到实例”

Question

Working on a countdown when i get this error when trying to run this code:

error code: Unrecognized selector sent to instance

class ViewController: UIViewController, UITableViewDelegate {

@IBOutlet weak var datePicker: UIDatePicker!
@IBOutlet weak var label: UILabel!

weak var timer: NSTimer?

let formatter: NSDateComponentsFormatter = {
    let _formatter = NSDateComponentsFormatter()
    _formatter.allowedUnits = [.Year, .Month, .Day, .Hour]
    _formatter.unitsStyle = .Full

    return _formatter
}()

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    datePicker.date = NSDate().dateByAddingTimeInterval(1000) // initialize it to whatever you want
}

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

    timer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: "didFireTimer:", userInfo: nil, repeats: true)
}

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

    timer?.invalidate()
}

func didFireTimer(timer: NSTimer) {
    label.text = formatter.stringFromDate(NSDate(), toDate: datePicker.date)


}

The whole error message:

2015-11-23 22:34:45.148 DatePicker xxTestxx[19009:4738036] -[UIView setDate:]: unrecognized selector sent to instance 0x7feaf8f9cbf0
2015-11-23 22:34:45.151 DatePicker xxTestxx[19009:4738036] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIView setDate:]: unrecognized selector sent to instance 0x7feaf8f9cbf0'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000102e75f45 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x0000000104b99deb objc_exception_throw + 48
    2   CoreFoundation                      0x0000000102e7e56d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
    3   CoreFoundation                      0x0000000102dcbeea ___forwarding___ + 970
    4   CoreFoundation                      0x0000000102dcba98 _CF_forwarding_prep_0 + 120
    5   DatePicker xxTestxx                 0x0000000102c8e944 _TFC19DatePicker_xxTestxx14ViewController11viewDidLoadfS0_FT_T_ + 260
    6   DatePicker xxTestxx                 0x0000000102c8e9e2 _TToFC19DatePicker_xxTestxx14ViewController11viewDidLoadfS0_FT_T_ + 34
    7   UIKit                               0x0000000103824cc4 -[UIViewController loadViewIfRequired] + 1198
    8   UIKit                               0x0000000103825013 -[UIViewController view] + 27
    9   UIKit                               0x00000001036fe51c -[UIWindow addRootViewControllerViewIfPossible] + 61
    10  UIKit                               0x00000001036fec05 -[UIWindow _setHidden:forced:] + 282
    11  UIKit                               0x00000001037104a5 -[UIWindow makeKeyAndVisible] + 42
    12  UIKit                               0x000000010368a396 -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 4131
    13  UIKit                               0x00000001036909c3 -[UIApplication _runWithMainScene:transitionContext:completion:] + 1750
    14  UIKit                               0x000000010368dba3 -[UIApplication workspaceDidEndTransaction:] + 188
    15  FrontBoardServices                  0x0000000106a28784 -[FBSSerialQueue _performNext] + 192
    16  FrontBoardServices                  0x0000000106a28af2 -[FBSSerialQueue _performNextFromRunLoopSource] + 45
    17  CoreFoundation                      0x0000000102da2011 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    18  CoreFoundation                      0x0000000102d97f3c __CFRunLoopDoSources0 + 556
    19  CoreFoundation                      0x0000000102d973f3 __CFRunLoopRun + 867
    20  CoreFoundation                      0x0000000102d96e08 CFRunLoopRunSpecific + 488
    21  UIKit                               0x000000010368d4f5 -[UIApplication _run] + 402
    22  UIKit                               0x000000010369230d UIApplicationMain + 171
    23  DatePicker xxTestxx                 0x0000000102c9120d main + 109
    24  libdyld.dylib                       0x00000001056a192d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) 

Answer 1

The error message is very clear that you are calling setDate on UIView .

In your code, the only place setDate is called is this line

 datePicker.date = NSDate().dateByAddingTimeInterval(1000) // initialize it to whatever you want

(Note: Compiler will compile x.date = y to x.setDate(y) )

Which means datePicker.date is UIView instead of UIDatePicker .

You have to change the nib file in interface builder to make sure the view that connect to datePicker is UIDatePicker instead of UIView