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Questions tagged [dispatch-async]

437 questions
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ALAssetLibrary performBlockAndWait (GUI hang issues)

I am writing an image uploader which indexes the camera roll on certain events, creates jobs, and then writes those jobs into CoreData. Another thread reads from CoreData to upload the images. I keep getting UI freezes. Event though the GUI is…
VaporwareWolf
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Does dispatch_async block to serial queue keeps order?

When I submit two blocks into a serial queue by dispatch_async, does it assure the second one runs after the first one: dispatch_async(serial_queue, b1); dispatch_async(serial_queue, b2); can we assure b1 runs before b2? Below is full source code…
AnkyHe
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DispatchQueue.main.asyncAfter not delaying

My DispatchQueue.main.asyncAfter execution block does not wait to execute. I wrote a MacOS single view app. (xCode 12.0.1 (12A7300)). It has a for-loop that calls a function that downloads content from my server. I want to throttle the requests. I…
sebrenner
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UILabel text is not updated even in MainThread

UILabel.text is not updated inside the main thread. labelOne is updated but labelTwo which is to show translated word is not updated. When I print translatedWord it prints right string to console but UILabel is not updated. datatask =…
Selçuk Yıldız
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Android: Dispatch queue

I am building an app that will make a web request whenever you scan a qr code. If you have internet available, making that request is easy. If we don't have internet, I want to put it onto a queue and make those requests whenever I have internet on…
Arham Akbar
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Nested async calls in Swift

I'm kind of new to programming in general, so I have this maybe simple question. Actually, writing helps me to identify the problem faster. Anyway, I have an app with multiple asynchronous calls, they are nested like…
Max Kraev
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Forcing all UIKit stuff to be done in the main thread

I am doing a complex application that has to do stuff on a lot of threads and frequently update the interface. So I have to add a lot of dispatch_async(dispatch_get_main_queue(), ^{ }); in the middle of the code to dispatch UI updates to the…
Duck
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React + Redux - dispatching an action in dumb component?

I started learning Redux and the whole idea looks neat, but after rebuilding my React app from "normal" to "redux-way" this problem came up. I have a list of if items that I build based on JSON from async call. Then every item on that list sends an…
Wordpressor
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Why does it take such a long time for UI to be updated from background thread?

I understand that all UI updates must be done from Main thread. But purely for the sake of deeper understanding how GCD and dispatch main work: I have a button that runs a network call and in its completionHandler I eventually…
mfaani
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Swift 3 : URL Image makes UITableView scroll slow issue

I have an extension to print image URL on UIImageView. But I think the problem is my tableView is so slow because of this extension. I think I need to open thread for it. How can I create a thread in this extension or do you know another solution to…
jorjj
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Swift 3: capture strong self in @escaping closure without asynchronous work

There is a protocol with the following declaration: typealias SuggestionSourceCallback = ([Suggestion]) -> () protocol SuggestionSource { func suggest(_ query: SuggestionQuery, callback: @escaping SuggestionSourceCallback) } Two classes…
Yevhen Dubinin
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Syntax to wrap a completion handler in dispatch async

I have a completion handler that I need to assign to a property, but I want it to execute asynchronously. If I didn't have that requirement, I would write: request.completionBlock = completionBlock But since I have this requirement, I have to…
KPM
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Get a thread by name/label in Objective-C

I would like to know if there is a way in Objective-C to get a thread by its name or label? dispatch_queue_t newQueue = dispatch_queue_create(@"NameOfTheQueue", NULL); This creates the queue. So, in another module, is there a way to get that…
Jeff
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dispatch_async vs dispatch_sync in fetch data. Swift

After reading so many posts about parallel and concurrent, I still confuse what is the proper way to fetch data. For example, in my project, I have a button for user to fetch data. My code is something like below. var array = [Int]() func…
Pak Ho Cheung
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"This application is modifying the autolayout engine" error (Swift iOS)

I am stuck figuring out how to fix an "This application is modifying the autolayout engine from a background thread" error. Any help is greatly appreciated. I tried the approach outlined from this similar question to use…
Ben
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