ios - 来自 CNContactStore 请求访问的错误 "A promise was finished incorrectly"

Question

我正在构建一个 UI 来请求访问 CNContactStore 并处理用户之前(并且可能错误地)拒绝访问的情况。当我检测到当前状态为 .denied 时，我会显示一个 UIAlertController，它会解释并提议将它们带到应用程序设置以允许访问。

在当前状态为 .denied 的情况下调用 store.requestAccess() 时，应用程序会崩溃并显示两个错误:1) “A promise was finished with a nil error”。和 2) “一个 promise 被错误地完成了。”。调用堆栈如下所示。

我不擅长解释调用堆栈，但我认为错误来自 CNContactStore 内部。我不清楚我能做些什么来防止这个错误。

编辑:我根本没有在我的应用程序中使用 promise 链。

EDIT2:上面明确说明了我的代码中发生错误的确切位置。

import UIKit
import Contacts
import ContactsUI

final class ContactsAppHelper {

static let shared = ContactsAppHelper()

var store = CNContactStore()

func checkAccessStatus(_ completionHandler: @escaping (_ accessGranted: Bool) -> Void) {

    let authorizationStatus = CNContactStore.authorizationStatus(for: .contacts)

    switch authorizationStatus {
    case .authorized:
        completionHandler(true)
    case .denied, .notDetermined:
        store.requestAccess(for: .contacts, completionHandler: { (access, accessError) -> Void in
            if access {
                completionHandler(access)
            }
            else {
                print("access denied")
                DispatchQueue.main.sync {
                    self.showSettingsAlert(completionHandler)
                }
            }
        })
    default:
        completionHandler(false)
    }
}

private func showSettingsAlert(_ completionHandler: @escaping (_ accessGranted: Bool) -> Void) {

    let msg = "This app requires access to Contacts to proceed. Would you like to open settings and grant permission?"
    let alert = UIAlertController(title: nil, message: msg, preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "Open Settings", style: .default) { action in
        completionHandler(false)
        UIApplication.shared.open(URL(string: UIApplication.openSettingsURLString)!)
    })
    alert.addAction(UIAlertAction(title: "Cancel", style: .cancel) { action in
        completionHandler(false)
    })
    let vc = UIApplication.getPresentedViewController()
    vc!.present(alert, animated: true)
}
}


extension UIApplication{
class func getPresentedViewController() -> UIViewController? {
    var presentViewController = UIApplication.shared.keyWindow?.rootViewController
    while let pVC = presentViewController?.presentedViewController
    {
        presentViewController = pVC
    }
    return presentViewController
}
}

这些是产生的调用堆栈:

2019-06-14 15:59:12.220116-0700 Sales Networker[805:28798] [Rx] A promise was finished with a nil error.
2019-06-14 15:59:12.226500-0700 Sales Networker[805:28798] [Rx] Call stack: (
    0   ContactsFoundation                  0x000000012242312a -[CNFuture finishWithError:] + 52
    1   Contacts                            0x000000010e0c2a82 __55-[CNDataMapperContactStore requestAccessForEntityType:]_block_invoke_2 + 187
    2   Contacts                            0x000000010e0ffc71 +[CNAuthorization requestAccessForEntityType:completionHandler:] + 77
    3   Contacts                            0x000000010e072c44 -[CNXPCDataMapper requestAccessForEntityType:completionHandler:] + 123
    4   Contacts                            0x000000010e0c299a __55-[CNDataMapperContactStore requestAccessForEntityType:]_block_invoke + 174
    5   libsystem_trace.dylib               0x000000011269cf00 os_activity_apply_f + 66
    6   Contacts                            0x000000010e116d52 -[_CNContactsLogger requestingAccessForContacts:] + 225
    7   Contacts                            0x000000010e0c28a4 -[CNDataMapperContactStore requestAccessForEntityType:] + 177
    8   Contacts                            0x000000010e09b77f -[CNContactStore requestAccessForEntityType:completionHandler:] + 54
    9   Sales Networker                     0x000000010ccaadc7 $s15Sales_Networker17ContactsAppHelperC17checkAccessStatusyyySbcF + 535
    10  Sales Networker                     0x000000010cce9673 $s15Sales_Networker24OnBoardingViewControllerC17rightButtonTappedyySo8UIButtonCF + 451
    11  Sales Networker                     0x000000010cce9ddc $s15Sales_Networker24OnBoardingViewControllerC17rightButtonTappedyySo8UIButtonCFTo + 60
    12  UIKitCore                           0x0000000119c7d204 -[UIApplication sendAction:to:from:forEvent:] + 83
    13  UIKitCore                           0x00000001196d2c19 -[UIControl sendAction:to:forEvent:] + 67
    14  UIKitCore                           0x00000001196d2f36 -[UIControl _sendActionsForEvents:withEvent:] + 450
    15  UIKitCore                           0x00000001196d1eec -[UIControl touchesEnded:withEvent:] + 583
    16  UIKitCore                           0x0000000119cb5eee -[UIWindow _sendTouchesForEvent:] + 2547
    17  UIKitCore                           0x0000000119cb75d2 -[UIWindow sendEvent:] + 4079
    18  UIKitCore                           0x0000000119c95d16 -[UIApplication sendEvent:] + 356
    19  UIKitCore                           0x0000000119d66293 __dispatchPreprocessedEventFromEventQueue + 3232
    20  UIKitCore                           0x0000000119d68bb9 __handleEventQueueInternal + 5911
    21  CoreFoundation                      0x000000010ebd6be1 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    22  CoreFoundation                      0x000000010ebd6463 __CFRunLoopDoSources0 + 243
    23  CoreFoundation                      0x000000010ebd0b1f __CFRunLoopRun + 1231
    24  CoreFoundation                      0x000000010ebd0302 CFRunLoopRunSpecific + 626
    25  GraphicsServices                    0x0000000114a702fe GSEventRunModal + 65
    26  UIKitCore                           0x0000000119c7bba2 UIApplicationMain + 140
    27  Sales Networker                     0x000000010cca7f6b main + 75
    28  libdyld.dylib                       0x0000000112416541 start + 1
)
2019-06-14 15:59:12.236494-0700 Sales Networker[805:28798] [Rx] A promise was finished incorrectly.
2019-06-14 15:59:12.236582-0700 Sales Networker[805:28798] [Rx] Result: (null)
2019-06-14 15:59:12.236669-0700 Sales Networker[805:28798] [Rx] Error : (null)
2019-06-14 15:59:12.238150-0700 Sales Networker[805:28798] [Rx] Call stack: (
    0   ContactsFoundation                  0x0000000122422ed8 -[CNFuture finishWithResult:error:] + 290
    1   Contacts                            0x000000010e0c2a82 __55-[CNDataMapperContactStore requestAccessForEntityType:]_block_invoke_2 + 187
    2   Contacts                            0x000000010e0ffc71 +[CNAuthorization requestAccessForEntityType:completionHandler:] + 77
    3   Contacts                            0x000000010e072c44 -[CNXPCDataMapper requestAccessForEntityType:completionHandler:] + 123
    4   Contacts                            0x000000010e0c299a __55-[CNDataMapperContactStore requestAccessForEntityType:]_block_invoke + 174
    5   libsystem_trace.dylib               0x000000011269cf00 os_activity_apply_f + 66
    6   Contacts                            0x000000010e116d52 -[_CNContactsLogger requestingAccessForContacts:] + 225
    7   Contacts                            0x000000010e0c28a4 -[CNDataMapperContactStore requestAccessForEntityType:] + 177
    8   Contacts                            0x000000010e09b77f -[CNContactStore requestAccessForEntityType:completionHandler:] + 54
    9   Sales Networker                     0x000000010ccaadc7 $s15Sales_Networker17ContactsAppHelperC17checkAccessStatusyyySbcF + 535
    10  Sales Networker                     0x000000010cce9673 $s15Sales_Networker24OnBoardingViewControllerC17rightButtonTappedyySo8UIButtonCF + 451
    11  Sales Networker                     0x000000010cce9ddc $s15Sales_Networker24OnBoardingViewControllerC17rightButtonTappedyySo8UIButtonCFTo + 60
    12  UIKitCore                           0x0000000119c7d204 -[UIApplication sendAction:to:from:forEvent:] + 83
    13  UIKitCore                           0x00000001196d2c19 -[UIControl sendAction:to:forEvent:] + 67
    14  UIKitCore                           0x00000001196d2f36 -[UIControl _sendActionsForEvents:withEvent:] + 450
    15  UIKitCore                           0x00000001196d1eec -[UIControl touchesEnded:withEvent:] + 583
    16  UIKitCore                           0x0000000119cb5eee -[UIWindow _sendTouchesForEvent:] + 2547
    17  UIKitCore                           0x0000000119cb75d2 -[UIWindow sendEvent:] + 4079
    18  UIKitCore                           0x0000000119c95d16 -[UIApplication sendEvent:] + 356
    19  UIKitCore                           0x0000000119d66293 __dispatchPreprocessedEventFromEventQueue + 3232
    20  UIKitCore                           0x0000000119d68bb9 __handleEventQueueInternal + 5911
    21  CoreFoundation                      0x000000010ebd6be1 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    22  CoreFoundation                      0x000000010ebd6463 __CFRunLoopDoSources0 + 243
    23  CoreFoundation                      0x000000010ebd0b1f __CFRunLoopRun + 1231
    24  CoreFoundation                      0x000000010ebd0302 CFRunLoopRunSpecific + 626
    25  GraphicsServices                    0x0000000114a702fe GSEventRunModal + 65
    26  UIKitCore                           0x0000000119c7bba2 UIApplicationMain + 140
    27  Sales Networker                     0x000000010cca7f6b main + 75
    28  libdyld.dylib                       0x0000000112416541 start + 1
)

Answer 1

我测试了你的代码，发现这里发生了两件事。

首先是当状态已经是.denied 时调用requestAccess(for:completion:) 时，您会在控制台上得到一个非致命的堆栈跟踪.您可以忽略此问题，也可以仅在 .notDetermined 状态下请求访问权限。

第二个问题与主队列上的同步调度有关。由于某种原因，这会导致访问冲突。解决方案是使用异步 分派(dispatch)。无论如何都没有充分的理由阻塞调用队列。

func checkAccessStatus(_ completionHandler: @escaping (_ accessGranted: Bool) -> Void) {

    let authorizationStatus = CNContactStore.authorizationStatus(for: .contacts)

    switch authorizationStatus {
    case .authorized:
        completionHandler(true)
    case .denied:
        self.showSettingsAlert(completionHandler)
    case .notDetermined:
        store.requestAccess(for: .contacts, completionHandler: { (access, accessError) -> Void in
            if access {
                completionHandler(access)
            }
            else {
                print("access denied")
                self.showSettingsAlert(completionHandler)
            }
        })
    default:
        completionHandler(false)
    }
}


private func showSettingsAlert(_ completionHandler: @escaping (_ accessGranted: Bool) -> Void) {

    let msg = "This app requires access to Contacts to proceed. Would you like to open settings and grant permission?"
    let alert = UIAlertController(title: nil, message: msg, preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "Open Settings", style: .default) { action in
        completionHandler(false)
        UIApplication.shared.open(URL(string: UIApplication.openSettingsURLString)!)
    })
    alert.addAction(UIAlertAction(title: "Cancel", style: .cancel) { action in
        completionHandler(false)
    })
    DispatchQueue.main.async {
        if let vc = UIApplication.getPresentedViewController() {
            vc.present(alert, animated: true)
        } else {
             completionHandler(false)
        }
    }
}