i recieved many crash after i received pasteboard content changed notification

Question

i recieved many crash after i received pasteboard content changed notification. i just monitor the change of pasteboard, and try to recognize the text content.

here is my code:

        class PasteboardMonitor {

            init() {
                addPasteboardMonitor()
            }

            func addPasteboardMonitor() {

                handleContentFromPasteBoard(conent: UIPasteboard.general.string, identifier: "\(UIPasteboard.general.changeCount)")

                NotificationCenter.default.addObserver(self, selector: #selector(didReceivedPasteboardNotification(noti:)), name: UIPasteboard.changedNotification, object: nil)
                NotificationCenter.default.addObserver(self, selector: #selector(didReceivedPasteboardNotification(noti:)), name: UIApplication.willEnterForegroundNotification, object: nil)
                NotificationCenter.default.addObserver(self, selector: #selector(didReceivedApplicationNotification), name: UIApplication.willResignActiveNotification, object: nil)
            }

           func handleContentFromPasteBoard(conent: String?, identifier: String? = nil) {
                //handle content
                ...
           }

           @objc func didReceivedPasteboardNotification(noti: Notification) {
                handleContentFromPasteBoard(conent: UIPasteboard.general.string, identifier: "\(UIPasteboard.general.changeCount)")
            }

the crash log is:

Crashed: com.apple.UIKit.pasteboard.cache-queue
0 libsystem_pthread.dylib 0x1963b5a38 ___chkstk_darwin + 64
1 libdispatch.dylib 0x19635f49c _dispatch_mach_send_and_wait_for_reply + 440
2 libdispatch.dylib 0x19635f904 dispatch_mach_send_with_result_and_wait_for_reply + 56
3 libxpc.dylib 0x19629f594 xpc_connection_send_message_with_reply_sync + 240
4 Foundation 0x196ba51fc NSXPCCONNECTION_IS_WAITING_FOR_A_SYNCHRONOUS_REPLY + 16
5 Foundation 0x19696b090 -[NSXPCConnection _sendInvocation:orArguments:count:methodSignature:selector:withProxy:] + 2704
6 Foundation 0x19696a40c -[NSXPCConnection _sendSelector:withProxy:arg1:] + 128
7 Foundation 0x196bac2ac _NSXPCDistantObjectSimpleMessageSend1 + 40
8 Pasteboard 0x1ac476aac -[PBServerConnection localGeneralPasteboard:]
9 UIKitCore 0x19a6c3428 _getTemporaryLocalGeneralPasteboard + 64
10 UIKitCore 0x19a6c2444 _pasteboardCacheQueue_existingItemCollectionWithName + 152
11 UIKitCore 0x19a6c2160 __59+[_UIConcretePasteboard _pasteboardNamed:createIfNotFound:]_block_invoke + 236
12 libdispatch.dylib 0x196349fd8 _dispatch_client_callout + 20
13 libdispatch.dylib 0x1963567f4 _dispatch_lane_barrier_sync_invoke_and_complete + 60 ...
218 UIKitCore 0x19a6c1fcc +[_UIConcretePasteboard _pasteboardNamed:createIfNotFound:] + 396
219 TovApp 0x1014e4a54 PasteboardMonitor.didReceivedPasteboardNotification(noti:) + 123 (PasteboardMonitor.swift:123)
220 TovApp 0x1014e4c4c @objc PasteboardMonitor.didReceivedPasteboardNotification(noti:) + 4351249484 (:4351249484)
221 Foundation 0x196a6effc __57-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_2 + 28
222 CoreFoundation 0x1965fc99c CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER + 28
223 CoreFoundation 0x1965fc9ec ___CFXRegistrationPost1_block_invoke + 68
224 CoreFoundation 0x1965fbce4 _CFXRegistrationPost1 + 396
225 CoreFoundation 0x1965fb97c ___CFXNotificationPost_block_invoke + 108
226 CoreFoundation 0x196574910 -[_CFXNotificationRegistrar find:object:observer:enumerator:] + 1424
227 CoreFoundation 0x1965fb2ac _CFXNotificationPost + 1268
228 Foundation 0x19695db8c -[NSNotificationCenter postNotificationName:object:userInfo:] + 64
229 UIKitCore 0x19a6c1cd4 _sendPasteboardChangedNotification + 96
230 UIKitCore 0x19a6c1fcc +[_UIConcretePasteboard _pasteboardNamed:createIfNotFound:] + 396
231 TovApp 0x1014e4a54 PasteboardMonitor.didReceivedPasteboardNotification(noti:) + 123 (PasteboardMonitor.swift:123)
232 TovApp 0x1014e4c4c @objc PasteboardMonitor.didReceivedPasteboardNotification(noti:) + 4351249484 (:4351249484)
233 Foundation 0x196a6effc __57-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_2 + 28
234 CoreFoundation 0x1965fc99c CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER + 28
235 CoreFoundation 0x1965fc9ec ___CFXRegistrationPost1_block_invoke + 68
236 CoreFoundation 0x1965fbce4 _CFXRegistrationPost1 + 396
237 CoreFoundation 0x1965fb97c ___CFXNotificationPost_block_invoke + 108
238 CoreFoundation 0x196574910 -[_CFXNotificationRegistrar find:object:observer:enumerator:] + 1424
239 CoreFoundation 0x1965fb2ac _CFXNotificationPost + 1268
240 Foundation 0x19695db8c -[NSNotificationCenter postNotificationName:object:userInfo:] + 64
241 UIKitCore 0x19a6c1cd4 _sendPasteboardChangedNotification + 96
242 UIKitCore 0x19a6c1fcc +[_UIConcretePasteboard _pasteboardNamed:createIfNotFound:] + 396
243 TovApp 0x1014e4a54 PasteboardMonitor.didReceivedPasteboardNotification(noti:) + 123 (PasteboardMonitor.swift:123)
244 TovApp 0x1014e4c4c @objc PasteboardMonitor.didReceivedPasteboardNotification(noti:) + 4351249484 (:4351249484)
245 Foundation 0x196a6effc __57-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_2 + 28
246 CoreFoundation 0x1965fc99c CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER + 28
247 CoreFoundation 0x1965fc9ec ___CFXRegistrationPost1_block_invoke + 68
248 CoreFoundation 0x1965fbce4 _CFXRegistrationPost1 + 396
249 CoreFoundation 0x1965fb97c ___CFXNotificationPost_block_invoke + 108
250 CoreFoundation 0x196574910 -[_CFXNotificationRegistrar find:object:observer:enumerator:] + 1424
251 CoreFoundation 0x1965fb2ac _CFXNotificationPost + 1268
252 Foundation 0x19695db8c -[NSNotificationCenter postNotificationName:object:userInfo:] + 64
253 UIKitCore 0x19a6c1cd4 _sendPasteboardChangedNotification + 96
254 UIKitCore 0x19a6c1fcc +[_UIConcretePasteboard _pasteboardNamed:createIfNotFound:] + 396
255 TovApp 0x1014e4a54 PasteboardMonitor.didReceivedPasteboardNotification(noti:) + 123 (PasteboardMonitor.swift:123)

do anybody know why this occurs? and how to fix it? thanks.

no, the crash logs collect by firebase from product enviroment — jianchengpan

Olha Olha · Accepted Answer · 2020-05-15T10:16:28

Your code related to NotificationCenter looks risky.

Try:

Ensuring you add observer only once:

var observersAdded: Bool = false

func addPasteboardMonitor() {
    ...
    if !observersAdded {
        NotificationCenter.default.addObserver(self ....
        observersAdded = true
    }
    ...
}

Removing observers in the destructor of PasteboardMonitor: NotificationCenter.default.removeObserver

i recieved many crash after i received pasteboard content changed notification

1 Answers