grand-central-dispatch

问题 I have a singelton class which will be create in the app delegate. When i run XCTTests then its get create a second time. + (instancetype)urlSchemeManager { static dispatch_once_t onceToken; static UrlSchemeManager* _sharedInstance; dispatch_once(&onceToken, ^{ _sharedInstance = [UrlSchemeManager new]; }); return _sharedInstance; } This is resulting in two different instances. This was no problem if i just use it for unit test. But in the integration test, when i register an observer for

问题 I have a singelton class which will be create in the app delegate. When i run XCTTests then its get create a second time. + (instancetype)urlSchemeManager { static dispatch_once_t onceToken; static UrlSchemeManager* _sharedInstance; dispatch_once(&onceToken, ^{ _sharedInstance = [UrlSchemeManager new]; }); return _sharedInstance; } This is resulting in two different instances. This was no problem if i just use it for unit test. But in the integration test, when i register an observer for

问题 I have a singelton class which will be create in the app delegate. When i run XCTTests then its get create a second time. + (instancetype)urlSchemeManager { static dispatch_once_t onceToken; static UrlSchemeManager* _sharedInstance; dispatch_once(&onceToken, ^{ _sharedInstance = [UrlSchemeManager new]; }); return _sharedInstance; } This is resulting in two different instances. This was no problem if i just use it for unit test. But in the integration test, when i register an observer for

问题 I have a singelton class which will be create in the app delegate. When i run XCTTests then its get create a second time. + (instancetype)urlSchemeManager { static dispatch_once_t onceToken; static UrlSchemeManager* _sharedInstance; dispatch_once(&onceToken, ^{ _sharedInstance = [UrlSchemeManager new]; }); return _sharedInstance; } This is resulting in two different instances. This was no problem if i just use it for unit test. But in the integration test, when i register an observer for

问题 I have a singelton class which will be create in the app delegate. When i run XCTTests then its get create a second time. + (instancetype)urlSchemeManager { static dispatch_once_t onceToken; static UrlSchemeManager* _sharedInstance; dispatch_once(&onceToken, ^{ _sharedInstance = [UrlSchemeManager new]; }); return _sharedInstance; } This is resulting in two different instances. This was no problem if i just use it for unit test. But in the integration test, when i register an observer for

问题 I have a few labels bound to a few variables that are modified in other threads via GCD. Now I've read that cocoa bindings are not thread safe but my app is running fine (the UI updates when the values of the variables are updated in a background thread) Would it be the correct way to do the calculations in the background thread and if I need to change the variable value make this via DispatchQueue.main.sync() { self.variable = newValue } ? If cocoa bindings are not thread safe, why I never

问题 I am trying to use dispatch groups to wait for two asynchronous processes to finish. However the second asynchronous function loops to the amount of messages I have in my database. The code below crashes because the number of dispatch is not balanced since dispatch leave is higher than the number of dispatch enters due to the multiple executions of the second asynchronous function. Is there a different way to implement dispatch groups in this case. dispatch_group_enter(dispatch_group) ref

问题 I'd like to understand for below case if it's needed to check whether callbackQueue is current queue. Please help me clear these scenarios, about what could happen if current queue is callback queue: callbackQueue is main queue. callbackQueue is concurrent queue. callbackQueue is serial queue. - (void)fetchWithCallbackQueue:(dispatch_queue_t)callbackQueue { dispatch_async(callbackQueue, ^{ }); } 回答1: I highly recommend you to watch these videos. Then go through the examples I provided and

问题 In my example code below, I call complete(false) on failure. However, since I'm using a DispatchGroup object to make sure all asynchronous requests are complete, I cannot just call syncGroup.leave() on failure, as the notify will be called, which contains complete(true) , making this function return true , when it should be returning false for failure. Am I correct in not calling syncGroup.leave() on failure to complete my function correctly? Or should I be calling syncGroup.leave() and

问题 import Dispatch class SynchronizedArray<T> { private var array: [T] = [] private let accessQueue = DispatchQueue(label: "SynchronizedArrayAccess", attributes: .concurrent) var get: [T] { accessQueue.sync { array } } func append(newElement: T) { accessQueue.async(flags: .barrier) { self.array.append(newElement) } } } If I run the following code, 10,000 elements are appended to the array as expected even if I am reading concurrently: DispatchQueue.concurrentPerform(iterations: 10000) { i in _