Feature/add extension to support tests #96
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…pletion block execution
Problem was that “isReady” property change KVO event was generated on every “state” property change, but in most of cases state-change doesn’t mean isReady-change. After every isReady KVO event, isReady property is read by NSOperations runtime. Since state-change (and as a result isReady KVO event) may happen and happens in multiple threads, isReady-getter is called from multiple threads too. The problem happens when isReady is called from multiple threads around the same time: the first call return False, but the second one returns True. Since there are two threads, first call can be actually finished after second one. In this case NSOperations runtime receivce isReady state value in the order like [false, false… false, true, false]. In this situation operations is actually ready, but it is not executed by queue (looks like because last isReady state was False). To fix the described problem idea is to stop bombing with KVO events. Actually during NSOperation life isReady is changed only once from false -> true. So ideally is to have only one KVO event when operations is really ready.
jjatie
reviewed
Nov 14, 2018
| @@ -96,7 +98,9 @@ open class OperationQueue: Foundation.OperationQueue { | |||
| */ | |||
| operation.addCompletionBlock { [weak self, weak operation] in | |||
| guard let queue = self, let operation = operation else { return } | |||
| queue.delegate?.operationQueue?(queue, operationDidFinish: operation, withErrors: []) | |||
| if let delegate = queue.delegate { | |||
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Why write something more verbose? Optional chaining already indicated that we are only performing the delegate if the delegate exists.
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