logger.swift

private let datadogQueue: DispatchQueue = DispatchQueue(label: "foo.datadog")

class Logger {
    fileprivate var buffer = [NSDictionary]()
    fileprivate var backgroundTaskIdentifier: UIBackgroundTaskIdentifier = UIBackgroundTaskIdentifier.invalid
    fileprivate var observer: NSObjectProtocol?
    // ...
    
    init() {
        // ...
        // This ensures when the user quits the app or puts in background we send the logs to server
        observer = NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: "UIApplicationWillResignActiveNotification"), object: nil, queue: nil, using: {
            [unowned self] note in
            let tmpbuffer = self.buffer
            self.buffer = [NSDictionary]()
            self.backgroundTaskIdentifier = UIApplication.shared.beginBackgroundTask(withName: "saveDatadogLogRecords",
                                                                                     expirationHandler: {
                                                                                        self.endBackgroundTask()
            })
            self.sendLogsInBuffer(buffer: tmpbuffer)
        })
    }
    
    deinit {
        if let observer = observer {
            NotificationCenter.default.removeObserver(observer)
        }
    }
    
    func log<T>( _ message: @autoclosure () -> T, level: LogLevel, filename: String, line: Int) {
        // logic to convert given parameters to a dictionary
        addLogToBuffer(dict)
    }
    
    private func addLogToBuffer(_ dict: NSDictionary) {
        datadogQueue.async {
            self.buffer.append(dict)
            if self.buffer.count > DatadogConfig.maxEntriesInBuffer { // DatadogConfig.maxEntriesInBuffer = 25 entries
                let tmpbuffer = self.buffer
                self.buffer = [NSDictionary]()
                self.sendLogsInBuffer(buffer: tmpbuffer)
            }
        }
    }
    
    private func sendLogsInBuffer(buffer: [NSDictionary]) {
        // logic to send logs to server
    }
    
    private func endBackgroundTask() {
        if self.backgroundTaskIdentifier != UIBackgroundTaskIdentifier.invalid {
            let value = UIBackgroundTaskIdentifier(rawValue: self.backgroundTaskIdentifier.rawValue)
            UIApplication.shared.endBackgroundTask(value)
            self.backgroundTaskIdentifier = UIBackgroundTaskIdentifier.invalid
            print("Ending background task")
        }
    }
}

trace

Crashed: slimlogger.datadog
0  libobjc.A.dylib                0x18339ebe8 objc_retain + 8
1  libswiftCore.dylib             0x1b1aa6c78 swift::metadataimpl::ValueWitnesses<swift::metadataimpl::ObjCRetainableBox>::initializeWithCopy(swift::OpaqueValue*, swift::OpaqueValue*, swift::TargetMetadata<swift::InProcess> const*) + 24
2  libswiftCore.dylib             0x1b1a9af50 swift_arrayInitWithCopy + 120
3  SpringboardRetail              0x10045f814 specialized _ArrayBuffer._copyContents(subRange:initializing:) (<compiler-generated>)
4  SpringboardRetail              0x10045eeb0 specialized _ArrayBufferProtocol._arrayOutOfPlaceUpdate(_:_:_:_:) (<compiler-generated>)
5  SpringboardRetail              0x10045ecb0 specialized Array._copyToNewBuffer(oldCount:) (<compiler-generated>)
6  SpringboardRetail              0x10045d16c closure #1 in SlimDatadogDestination.addLogToBuffer(_:) (<compiler-generated>)
7  SpringboardRetail              0x1004607b0 thunk for @escaping @callee_guaranteed () -> () (<compiler-generated>)