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Questions tagged [nslock]

An NSLock object is used to coordinate the operation of multiple threads of execution within the same application. An NSLock object can be used to mediate access to an application’s global data or to protect a critical section of code, allowing it to run atomically.

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How to utilize NSLock to prevent a function from firing twice?

I current have a set of asynchronous functions that are both called in the viewDidLoad(). At the end of each function is a bool that is set from false to true upon completion of the function. There is also a conditional statement checking both…
Runeaway3
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Cocoa thread synchronisation when using [ALAssetsLibrary enumerateGroupsWithTypes:]

I have recently, like a few people, discovered that [ALAssetsLibrary enumerateGroupsWithTypes] likes to run its blocks on another thread. What a shame that Apple didn't document that :-) In my current circumstance I need to wait for the enumeration…
Martin Cowie
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NSLock - should just block when locking a locked lock?

I have a loop which starts with a [lock lock]; because in the body of the loop I am creating another thread which needs to finish before the loop runs again. (The other thread will unlock it when finished). However on the second loop I get the…
Nippysaurus
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How to execute a lock that waits until an animation completes?

I am implementing a health bar that animates via user input. These animations make it go up or down by a certain amount (say 50 units) and are the result of a button press. There are two buttons. Increase and Decrease. I want to execute a lock on…
Black Orchid
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How to lock an NSLock on a specific thread

I have a property @property NSLock *myLock And I want to write two methods: - (void) lock and - (void) unlock These methods lock and unlock myLock respectively and they need to do this regardless of what thread or queue called them. For instance,…
Nosrettap
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ALAssetsLibrary enumerateGroupsWithTypes: - Thread synchronization

I'm using [ALAssetsLibrary enumerateGroupsWithTypes:] to store the ALAssets in an array. As this is an asynchronous operation, I need to wait for it to finish before continuing my work. I read Cocoa thread synchronisation when using [ALAssetsLibrary…
Leary
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Lock and unlock a semaphore from different threads in Cocoa

I need to use some kind of semaphore to protect the access to a mutex zone, but I need this zone to span multiple threads. This is what I found in the documentation: Warning: The NSLock class uses POSIX threads to implement its locking …
Luca Carlon
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NSLock.lock() executed while lock already held?

I'm reviewing some Alamofire sample Retrier code: func should(_ manager: SessionManager, retry request: Request, with error: Error, completion: @escaping RequestRetryCompletion) { lock.lock() ; defer { lock.unlock() } if let…
Marcus Leon
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IOS SDK - NSLock message: "unlocked from thread which did not lock it"

I´m getting this error using NSLock which I tried to circumvent by using unlockWithCondition (using NSConditionLock), but regardless I get the same result: * Break on _NSLockError() to debug. * -[NSLock unlock]: lock ( '(null)') unlocked from…
ZiggyST
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Safe to use NSLock on main thread?

I have a global variable that is accessed from multiple threads, including from the main thread. I’d like to use NSLock because it’s faster than GCD. Here’s what I’m trying to do: struct SynchronizedLock { private var _value: Value …
TruMan1
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Not using NSLock correctly, but still seems to work

I had issues with thread safety. I have a queue that when I modified the contents caused errors across threads. I hadn't used locks before, but thought I try. I added a lock around all code that manipulated the backing NSMutableArray for my…
Brian
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NSLock "controller" class

I'm writing a multithreaded application for iPhone, and I'm using NSLock's to make sure that some operations (such as loading sounds from file) will behave as atomic. To simplify acquiring locks from different parts of my application, I wrote…
Least
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iOS -- trying to setup a dictionary of locks

I have some code that takes an NSString as input and uses that string to create an object. I need to make sure that it does not operate on the same string twice, e.g. if called from different threads, or even if the same thread tries to do it…
William Jockusch
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What is the difference (advantage and disadvantage) between using DispatchGroup and NSRecursiveLock?

What is the difference (advantage and disadvantage) between using DispatchGroup and NSRecursiveLock? It looks like they are doing exactly the same thing.
Dmitry
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Swift: Understanding NSLock deadlock

Seeing this message in our logs using NSLock: *** -[NSLock lock]: deadlock ( '(null)') *** Break on _NSLockError() to debug. Does this mean that the application has encountered a fatal error and will stop working? Or is…
Marcus Leon
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