grand-central-dispatch Questions
2
Solved
I've been experimenting with GCD priorities recently. Here's the snippet of code that I've been working with.
for _ in 1...1000 {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_...
Speckle asked 30/8, 2016 at 18:51
2
Solved
I noticed that my app doesn't request permission to use the camera. After some experimentation I figured out that the piece of code used to check permission takes a very long time to complete. So I...
Impatience asked 29/1, 2015 at 12:0
6
Solved
The answers I've seen so far (1, 2, 3) recommend using GCD's dispatch_once thus:
var token: dispatch_once_t = 0
func test() {
dispatch_once(&token) {
print("This is printed only on the first...
Malkamalkah asked 10/12, 2015 at 13:51
5
Solved
From what I've read about Grand Central Dispatch, GCD does not do preemptive multitasking; it is all a single event loop. I'm having trouble making sense of this output. I have two queues just doin...
Selfheal asked 15/12, 2011 at 19:56
4
Solved
I am hitting a web service url 10 times and getting the response. I am using Alamofire and SwiftyJSON. This is my controller code
class ViewController: UIViewController {
let dispatchGroup = Dis...
Cringe asked 23/6, 2018 at 19:3
4
Solved
I want to display an ActivityIndicatorView in my app, but when I call the sync method from the main thread, the app crashes with the error: exc_bad_instruction (code=exc_i386_invop subcode=0x0)
I'm...
Corissa asked 20/10, 2016 at 12:35
2
Solved
I have converted existing Swift2.3 code to Swift3.0 using Xcode8 beta4. Xcode automatically convert syntax to Swift3.0, but it not able to create serial dispatch queue.
private let serialQueue = D...
Pellikka asked 6/9, 2016 at 9:5
1
Solved
In GCD I just call:
DispatchQueue.main.asyncAfter(deadline: .now() + someTimeInterval) { ... }
But we started to migrate to Structured Concurrency.
I tried the following code:
extension Task where...
Spherule asked 26/5, 2023 at 12:40
12
Solved
I have a method which should support being called from any queue, and should expect to.
It runs some code in a background thread itself, and then uses dispatch_get_main_queue when it returns a val...
Dia asked 4/7, 2013 at 16:38
2
I have a series of HTTP requests made sequentially using Alamofire in a list of functions called in a main function, runTask() that I want to have the ability to stop. So, I set up the runTask() fu...
Tied asked 3/10, 2018 at 20:28
4
Solved
All the libraries I have come across that provide Swift concurrency functionality either depend on an Objective-C library or are wrappers around the C based GCD. (iOS and OS X)
I'm just wondering ...
Paperboy asked 3/3, 2016 at 11:42
7
Solved
For the longest time I thought asynchronous was synonymous to running something on a background thread, while synchronous meant on the main thread (blocking UI updates and interactions). I understa...
Precognition asked 14/1, 2014 at 20:1
4
I want to run a block of code only once per instance.
Can I declare dispatch_once_t predicate as a member variable instead of static variable?
From GCD Reference, it is not clear to me.
The p...
Bangup asked 13/12, 2012 at 8:45
3
Solved
I am currently playing around with Grand Central Dispatch and discovered a class called DispatchWorkItem. The documentation seems a little incomplete so I am not sure about using it the right way. ...
Ischium asked 14/7, 2016 at 9:8
4
Solved
First I create a serial queue like this
static dispatch_queue_t queue = dispatch_queue_create("myQueue", DISPATCH_QUEUE_SERIAL);
then, at some unknown point in time a task gets added to the queu...
Selfmade asked 7/9, 2012 at 11:24
3
Solved
I am trying to implement a Thread-Safe PhoneBook object. The phone book should be able to add a person, and look up a person based on their name and phoneNumber. From an implementation perspective ...
Elum asked 5/3, 2018 at 0:24
2
Solved
I am facing an issue in using semaphores on iOS.
I am implementing a feature to execute a series of async methods sequentially, one after another in order.
let semaphore = DispatchSemaphore(value: ...
Intermit asked 29/8, 2022 at 17:11
1
I am trying to implement dispath group , to perform a sequence of operations , that should execute one after another. But the issue is all the tasks adding to the group are executing in parallel. P...
Repertory asked 9/8, 2022 at 14:17
10
If I have a serial queue, how can I, from the main thread, tell it to immediately stop execution and cancel all of its tasks?
Virg asked 3/8, 2011 at 15:11
9
Solved
In Apple docs, it says:
Important: You should never call the dispatch_sync or dispatch_sync_f
function from a task that is executing in the same queue that you are
planning to pass to the fun...
Stuckey asked 13/3, 2013 at 9:21
11
Solved
In my app I have a function that makes an NSRURLSession and sends out an NSURLRequest using
sesh.dataTaskWithRequest(req, completionHandler: {(data, response, error)
In the completion block for ...
Attribution asked 27/7, 2014 at 21:12
7
Solved
I'm moving my code from regular GCD to NSOperationQueue because I need some of the functionality. A lot of my code relies on dispatch_after in order to work properly. Is there a way to do something...
Flush asked 18/3, 2013 at 15:31
4
Ok so I have gone through a ton of questions and answers and I know the understanding of it, but when I am trying some code, I am getting some results that doesnt stand by those theories.
What I ...
Spiegel asked 8/6, 2017 at 7:24
3
Solved
I have a ViewController that has a collectionView inside of it. I display the contents of the collectionView's cells inside an ARSCNView.
When I set the ViewController's view property to the Mater...
Ganef asked 22/12, 2019 at 17:13
2
I had an error when sending data to a firebase database :
Access to fetch at 'https://us-central1-pwagram-f39a5.cloudfunctions.net/storePostData' from origin 'http://localhost:3030' has been blo...
Moffitt asked 18/1, 2020 at 9:37
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