grand-central-dispatch

I'm attempting to debug some iOS crash logs that contain the following error message: *** Terminating app due to uncaught exception 'NSDestinationInvalidException', reason: '*** -[SomeClass performSelector:onThread:withObject:waitUntilDone:modes:]: target thread exited while waiting for the perform The relevant section of the code is: - (void) runInvocationOnMyThread:(NSInvocation*)invocation { NSThread* currentThread = [NSThread currentThread]; if (currentThread != myThread) { //call over to the correct thread [self performSelector:@selector(runInvocationOnMyThread:) onThread:myThread

Is there a way to save the current value of a varible for later usage in a block? For example, for this Playground code: import UIKit import XCPlayground XCPlaygroundPage.currentPage.needsIndefiniteExecution = true class testClass { var i = 0 func test() { let dispatchTime: dispatch_time_t = dispatch_time(DISPATCH_TIME_NOW, Int64(Double(NSEC_PER_SEC)) * 5) dispatch_after(dispatchTime, dispatch_get_main_queue(), { self.test(self.i) }) i = 3 } func test(i: Int) { print("i: \(i)") } } let a = testClass() a.test() Is there a way to save the current value of i for dispatch_after in a way that I get

I am aiming for a serial download queue within NSOperation subclass using dispatch groups to manage async tasks. I have maxConcurrentOperationCount set to 1 i have defined my queue var GlobalDownloadQueue: DispatchQueue { return DispatchQueue.global(qos: DispatchQoS.QoSClass.background) } Then inside main() of NSOperation subclass i have defined my dispatch group, have 3 enters and 3 leaves, then a notify block. The notify block seems to be running at the right time, however there is still multiple instances of the NSOperation running at once. This is what the console is printing when i select

I am porting some code from C++ to Swift that used Grand Central Dispatch, and I am finding a curious error with dispatch_queue_create seemingly not working at all. For instance, in my C++ base class header, I would declare dispatch_queue_t m_WorkQ; and in the initializer, put m_ResultQ = dispatch_queue_create("com.myapp.mHitsUpdateQueue", 0); ... and everything was glorious. I've tried this in Swift, in my class, declaring this at class level: var resultQueue: dispatch_queue_t ... and in the initalizer, I have (among others) the line resultQueue = dispatch_queue_create("com.myapp

What's happening above: Initialize realm model from the received array of user data. Write all the models at once in the realm DB in the background thread. Realm model is getting updated if they already exist by creating a copy. Can anyone please guide me here about what I am doing wrong. 来源： https://stackoverflow.com/questions/55700998/enqueued-from-com-apple-main-thread-thread-1-crash-ios-swift-4-1

let downloadGroup = dispatch_group_create() var images = [UIImage]() var errors = [NSError]() dispatch_apply(UInt(urls.count), dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)) { (i) in dispatch_group_enter(downloadGroup) SimpleCache.sharedInstance.getImage(urls[Int(i)], completion: { (image, error) -> () in if let fullImage = image { images.append(fullImage) } else { if let err = error { DLog(err.description) errors.append(err) } } dispatch_group_leave(downloadGroup); }) } dispatch_group_notify(downloadGroup, dispatch_get_main_queue()) { completion(images, errors) } above is my code

Iam having problems with: dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0UL); concurrentQueue is nil on iOS 4.2.1 (device) but the same code works perfectly on another device which is running iOS 5.0.1. When I checked the header it says it's available since iOS 4.0, am I doing something wrong? The code below fetches images from the internet and works great in everything after 4.2.1 but not in 4.2.1, any ideas why? Can you create a concurrent queue some other way using GCD? - (void)imageFromURL:(NSString*)link { if ([link length] == 0) return;