Swift应用程序崩溃与CLLocationManager上发送到实例`的"无法识别的选择器"

Question

与StackOverflow上的许多其他问题类似,我unrecognized selector sent to instance在运行应用程序时遇到了错误.是什么让我的情况与众不同(我认为)是它用Swift编写的,并且常见的原因不是这里的原因.

在这个问题中,解决方案是将该视图的Identity Inspector中的"Custom Class"设置为响应类.我检查了这个情况(注意我在某个时候重命名了这个类,但它现在肯定设置为"ViewController").

我在下面包含堆栈跟踪以及代码ViewController.swift.您也可以在这里找到所有代码.我设法通过开始新鲜来避免这个问题,这使我能够解决我之前的问题.这个新的试验可以在这个分支中找到.但是,我想知道出了什么问题并解决了这个问题.

有些想法

我无法成功回答的一个问题是,是否CLLocationManagerDelegate需要一些必要的方法？但是因为我让它在另一个分支机构工作,我怀疑它没有必要.

2014-07-03 21:50:26.056 RowingTracker2[11416:60b] -[CLLocationManager requestWhenInUseAuthorization]: unrecognized selector sent to instance 0xa10c4a0
2014-07-03 21:50:26.059 RowingTracker2[11416:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[CLLocationManager     requestWhenInUseAuthorization]: unrecognized selector sent to instance 0xa10c4a0'
*** First throw call stack:
(
    0   CoreFoundation                      0x008831e4 __exceptionPreprocess + 180
1   libobjc.A.dylib                     0x01e2a8e5 objc_exception_throw + 44
2   CoreFoundation                      0x00920243 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
3   CoreFoundation                      0x0087350b ___forwarding___ + 1019
4   CoreFoundation                      0x008730ee _CF_forwarding_prep_0 + 14
5   RowingTracker2                      0x00003352 _TFC14RowingTracker214ViewController11viewDidLoadfS0_FT_T_ + 738
6   RowingTracker2                      0x000033a2 _TToFC14RowingTracker214ViewController11viewDidLoadfS0_FT_T_ + 34
7   UIKit                               0x0102f33d -[UIViewController loadViewIfRequired] + 696
8   UIKit                               0x0102f5d9 -[UIViewController view] + 35
9   UIKit                               0x00f4f267 -[UIWindow addRootViewControllerViewIfPossible] + 66
10  UIKit                               0x00f4f5ef -[UIWindow _setHidden:forced:] + 312
11  UIKit                               0x00f4f86b -[UIWindow _orderFrontWithoutMakingKey] + 49
12  UIKit                               0x00f5a3c8 -[UIWindow makeKeyAndVisible] + 65
13  UIKit                               0x00f0abc0 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 2097
14  UIKit                               0x00f0f667 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 824
15  UIKit                               0x00f23f92 -[UIApplication handleEvent:withNewEvent:] + 3517
16  UIKit                               0x00f24555 -[UIApplication sendEvent:] + 85
17  UIKit                               0x00f11250 _UIApplicationHandleEvent + 683
18  GraphicsServices                    0x031fff02 _PurpleEventCallback + 776
19  GraphicsServices                    0x031ffa0d PurpleEventCallback + 46
20  CoreFoundation                      0x007feca5 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
21  CoreFoundation                      0x007fe9db __CFRunLoopDoSource1 + 523
22  CoreFoundation                      0x0082968c __CFRunLoopRun + 2156
23  CoreFoundation                      0x008289d3 CFRunLoopRunSpecific + 467
24  CoreFoundation                      0x008287eb CFRunLoopRunInMode + 123
25  UIKit                               0x00f0ed9c -[UIApplication _run] + 840
26  UIKit                               0x00f10f9b UIApplicationMain + 1225
27  RowingTracker2                      0x00008021 top_level_code + 97
28  RowingTracker2                      0x0000805b main + 43
29  libdyld.dylib                       0x024ff701 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) 

ViewController.swift

import UIKit
import MapKit
import CoreLocation

class ViewController: UIViewController, MKMapViewDelegate, CLLocationManagerDelegate {
    @IBOutlet var mapview: MKMapView = nil
    var locationmgr : CLLocationManager!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        locationmgr = CLLocationManager()
        locationmgr.delegate = self
        locationmgr.requestWhenInUseAuthorization() ///< Offending line.
//        mapview.showsUserLocation = true
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

Answer 1

由于requestWhenInUseAuthorization方法仅适用于iOS 8(根据Apple文档),您必须将其包装:

SWIFT代码:

if (locationmgr.respondsToSelector(Selector("requestWhenInUseAuthorization"))) {
  locationmgr.requestWhenInUseAuthorization()
}

Objective-C也是如此:

if ([locationmgr respondsToSelector:@selector(requestWhenInUseAuthorization)]) {
    [locationmgr requestWhenInUseAuthorization];
}

Answer 2

此代码不会在iOS 7及更低版本上运行 - 根据文档,requestWhenInUseAuthorization仅适用于iOS 8:

可用性:

适用于iOS 8.0及更高版本.