nsoperation

问题 As the title suggests, what is the default value of the maxConcurrentOperationCount for NSOperationQueue? Is it set to a value of 1? 回答1: From the documentation, The maximum number of concurrent operations set explicitly on the receiver using the setMaxConcurrentOperationCount: method. If no value has been explicitly set, this method returns NSOperationQueueDefaultMaxConcurrentOperationCount by default . So it is NSOperationQueueDefaultMaxConcurrentOperationCount . If this is set, it will

问题 Today I've met one weird issue when I was trying to 'generalize' my 'CoreData importing operations'. It appeared that if I create a generic subclass of NSOperation the main() func won't be called. Simple example: class MyOperation<T: NSObject>: NSOperation { override func main() { println("My operation main was called") } } If you create an instance of this class and add it to the operationQueue you will see that it's main() isn't actually called. override func viewDidLoad() { super

问题 I have a long running loop I want to run in the background with an NSOperation . I'd like to use a block: NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{ while(/* not canceled*/){ //do something... } }]; The question is, how to I check to see if it's canceled. The block doesn't take any arguments, and operation is nil at the time it's captured by the block. Is there no way to cancel block operations? 回答1: Doh. Dear future googlers: of course operation is nil when

问题 I have an app that has to download multiple large files. I want it to download each file one by one sequentially instead of concurrently. When it runs concurrently the app gets overloaded and crashes. So. Im trying to wrap a downloadTaskWithURL inside a NSBlockOperation and then setting the maxConcurrentOperationCount = 1 on the queue. I wrote this code below but it didnt work since both files get downloaded concurrently. import UIKit class ViewController: UIViewController,

问题 I have an app that has to download multiple large files. I want it to download each file one by one sequentially instead of concurrently. When it runs concurrently the app gets overloaded and crashes. So. Im trying to wrap a downloadTaskWithURL inside a NSBlockOperation and then setting the maxConcurrentOperationCount = 1 on the queue. I wrote this code below but it didnt work since both files get downloaded concurrently. import UIKit class ViewController: UIViewController,

问题 I'm creating a simple game. I have the following code: - (void)doStuff { double delayInSeconds = [NSNumber randomFloatBetweenLowerBound:0.8f upperBound:2.6f]; // Own category on NSNumber returns random float. dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC)); dispatch_after(popTime, dispatch_get_main_queue(), ^(void){ // // Do stuff // if ([self shouldDoMoreStuff]) { [self doStuff]; } }); } This method is run in viewDidLoad , but it is also

问题 To avoid a memory leak when using NSBlockOperation in Objective-C, we would have to declare the variable as weak to be able to reference the block operation inside the block (to cancel if needed), typically like this: __weak NSBlockOperation *blockOp = [NSBlockOperation blockOperationWithBlock:^{ if (blockOp.cancelled) { ... } }]; But in Swift, when I try declare my NSBlockOpeartion as weak, it is always nil. weak var blockOp = NSBlockOperation() Without the weak reference, all is fine except

问题 I'm having problems to execute a https requests, if the request don't have any error i never get the message, this is a command line tool application and i have a plist to allow http requests, i always see the completion block. typealias escHandler = ( URLResponse?, Data? ) -> Void func getRequest(url : URL, _ handler : @escaping escHandler){ let session = URLSession.shared var request = URLRequest(url:url) request.cachePolicy = .reloadIgnoringLocalCacheData request.httpMethod = "GET" let

问题 I'm saving objects from network response in NSOperation . As I understand for merge MOC's changes from background threads to main I can use mergeChangesFromContextDidSaveNotification or performBlock with parent context. What should I prefer to use mergeChangesFromContextDidSaveNotification or performBlock ? What are the pros and cons of each merge method? NSOperation executed in background context. So when I call performBlock will be created new thread or not? 回答1: The answer depends very

问题 I'd like to make a custom class that extends NSOperation in order to make successful communication with another device by bluetooth. The question I have is how can I implement the main method of the class so that it will wait for an event triggered by the bluetooth? 回答1: Never use an infinite loop. It is not energy-efficient. As @lead_the_zeppelin said, use semaphore/mutex/etc. For example you may use dispatch_group functions like this: dispatch_group_t waitGroup = dispatch_group_create();