CODEWITHSUNDEEP
iosswiftrace-conditionnsoperationqueue
Anton Tropashko
Anton Tropashko

Reputation: 5806

What do I do with this exception tripped shortly after cancelling all operations on NSOperationQueue

Whenever I cancelAllOperations() I get this wonder message:

* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[__NSOperationInternal _start:]: something is trying to start the receiver simultaneously from more than one thread' *** First throw call stack: (0x1935321c0 0x191f6c55c 0x193532108 0x193f2b788 0x193ff8b00 0x1923bd1c0 0x1923cb444 0x1923c09a8 0x1923cd38c 0x1923cd0ec 0x1925c62b8 0x1925c5da4) libc++abi.dylib: terminating with uncaught exception of type NSException

This could not possibly be the very same bug discovered in 2008 in OSX and described here https://www.mikeash.com/pyblog/dont-use-nsoperationqueue.html ?

Though in my case this is a zero effort occurence: trips all the time.

  1. This accompanied by <myoperationnameishere> 0x17425e240 went isFinished=YES without being started by the queue it is in

  2. There is a huge number of operation types so I'm not listing them here.

However, all of them are derived from this class.

public class AsynchronousOperation: NSOperation {
    // MARK: - Types
    public enum State {
        case Ready, Executing, Finished
        func keyPath() -> String {
            switch self {
            case Ready:
                return "isReady"
            case Executing:
                return "isExecuting"
            case Finished:
                return "isFinished"
            }
        }
    }

    public override init() {
        state = State.Ready
        super.init()
    }

    // MARK: - Properties
    public var state = State.Ready {
        willSet {
            willChangeValueForKey(newValue.keyPath())
            willChangeValueForKey(state.keyPath())
        }
        didSet {
            Util.log("\(self.dynamicType) \(oldValue) -> \(state)", dc: [.Operation])
            didChangeValueForKey(oldValue.keyPath())
            didChangeValueForKey(state.keyPath())
        }
    }

    // MARK: - NSOperation
    override public var ready: Bool {
        return super.ready && state == .Ready
    }

    override public var executing: Bool {
        return state == .Executing
    }

    override public var finished: Bool {
        return state == .Finished
    }

    public override func cancel() {
        super.cancel()
        state = .Finished
    }
}

Upvotes: 2

Views: 1214

Answers (1)

Anton Tropashko
Anton Tropashko

Reputation: 5806

This accompanied by 0x17425e240 went isFinished=YES without being started by the queue it is in

was the clue. as well as this: NSOperationQueue not working in IOS5

I was setting isfinished to true in the cancel() method overridden in the operations further down the inheritance tree

and this is not correct for operations being cancelled that have not yet been started

now that this is taken care of the alarm bells are off

Upvotes: 3

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