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POEXC_BAD_ACCESS when checking an operation queue for duplicates
 

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  1. POEXC_BAD_ACCESS when checking an operation queue for duplicates
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    <p>I have an NSOperationQueue in my app that handles endpoint URL requests. To avoid adding duplicate requests, wherever possible I check the queue to see whether this endpoint call is already handled. </p> <p>For some reason, generally only when the endpoint operation queue is getting spammed like hell, but also randomly at other times (implying to me that it's a very uncommon race condition of some sort), I get an EXC_BAD_ACCESS when scanning my operation queue for duplicates. It happens on the line:</p> <pre><code> if (![endpointOperation.urlRequest respondsToSelector: @selector(URL)]) { </code></pre> <p>Here's the code:</p> <pre><code>-(BOOL)operationQueueContainsDuplicateOperations { for (EndpointOperation *endpointOperation in [EndpointOperationQueueManager instance].operationQueue.operations) { if (![endpointOperation.urlRequest respondsToSelector: @selector(URL)]) { return NO; } if (![self.urlRequest respondsToSelector: @selector(URL)]) { return NO; } if ([[endpointOperation.urlRequest.URL absoluteString] isEqualToString:[self.urlRequest.URL absoluteString]] &amp;&amp; (self.relatedProfileIds &amp;&amp; [endpointOperation.relatedProfileIds isEqualToArray:self.relatedProfileIds])) { return YES; } } return NO; </code></pre> <p>}</p> <p>I thought maybe the operation queue was being modified while this loop was in process but I don't know how that would happen - and when I receive the crash, I can view the contents of the relevant objects and they look fine. Any ideas?</p>
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    1. USNick Locking
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    1. COI would set a breakpoint on Objective-C exceptions and hope for a better error message than EXC_BAD_ACCESS.
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      1. POEXC_BAD_ACCESS when checking an operation queue for duplicates
      1. USPhillip Mills
    2. COMy guess is that you can't iterate the array on the queue because you'll end in a race condition issue (also the enumerator will be constantly changing it's pointer due the re-sort of the array). Why don't keep a NSDictionary with the list of endpoints in the queue? (So you can search for the key). Also you can apply KVO to the operations array, so that would be a safer approach :)
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      1. USrodchile
 

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