dispatch-queue

Run and Pause an ARSession in a specified period of time

由 |▌冷眼眸甩不掉的悲伤 提交于 2019-12-10 12:27:52
问题 I'm developing ARKit / Vision iOS app with gesture recognition. My app has a simple UI containing single UIView . There's no ARSCNView / ARSKView at all. I'm putting a sequence of captured ARFrames into CVPixelBuffer what then I use for VNRecognizedObjectObservation . I don't need any tracking data from a session. I just need currentFrame.capturedImage for CVPixelBuffer . And I need to capture ARFrames at 30 fps. 60 fps is excessive frame rate. preferredFramesPerSecond instance property is

How can i wait to receive a response from a DispatchWorkItem before moving on to the next request or next DispatchWorkItem in a Dispatch Queue

由 走远了吗. 提交于 2019-12-08 12:17:47
问题 I have an array of dispatch workItems, how to wait until one work is completed before i move on to the next work in the queue? func AsyncCalls(statusHandler: @escaping (String) -> Void){ var dispatchWorkItems : [DispatchWorkItem] = [] let categoryWorkItem = DispatchWorkItem { main { return statusHandler("Loading categories ") } self.modelView.getCategories(completion: { data,error in main { if data.isEmpty { return statusHandler("\(error )") }else{ return statusHandler("Done loading

Is there a specific way to append DispatchWorkItems to a DispatchQueue instead of re declaring them in code?

由 大憨熊 提交于 2019-12-08 09:31:17
问题 I have several Dispatch work items to execute on a queue i don't want to redeclare the codes, i want to pass them to an array or list of DispatchWorkItems and then inject it to a dispatch queue is there any way to achieve this ? func executeDispatchWorkItem(url: String, completion : @escaping (Result<String,Error>)-> Void,beganHandler : @escaping (String)-> Void){ do { beganHandler("\(url) Began to execute ") let content = try String(contentsOf:URL(string: url)!) completion(.success(content))

Multithreading executing multiple tasks in parallel in swift ios

由 和自甴很熟 提交于 2019-12-08 01:57:03
问题 I know creation of queues and able to execute single task but how can i execute multiple tasks in parallel. Concurrent Queue ----> let concurrentQueue = DispatchQueue(label: "com.some.concurrentQueue", attributes: .concurrent) concurrentQueue.async { //executable code } BackgroundQueue without priorities default---> DispatchQueue.global().async { //executable code } Backgroundqueue with priorities----> DispatchQueue.global(qos: .userInitiated).async { //.userInteractive .background .default

Multithreading executing multiple tasks in parallel in swift ios

由 非 Y 不嫁゛ 提交于 2019-12-06 14:22:24
I know creation of queues and able to execute single task but how can i execute multiple tasks in parallel. Concurrent Queue ----> let concurrentQueue = DispatchQueue(label: "com.some.concurrentQueue", attributes: .concurrent) concurrentQueue.async { //executable code } BackgroundQueue without priorities default---> DispatchQueue.global().async { //executable code } Backgroundqueue with priorities----> DispatchQueue.global(qos: .userInitiated).async { //.userInteractive .background .default .unspecified //executable code } Getting back to the main Queue ----> DispatchQueue.main.async { /

Difference between DispatchQueue types in swift

由 好久不见. 提交于 2019-12-06 13:35:36
问题 As I understand there are 3 types of DispatchQueue in swift: Main (serial) (Main Thread) Global (Concurrent) (Background Threads working in parallel) Custom (Concurrent or serial) And each one maybe work (asynch or synch) First question: Is it main queue working on UI thread only and not working on another thread? If the answer yes , how DispatchQueue.Main.async not blocking UI thread. If the answer No , what is the benefit of using DispatchQueue.global as long as DispatchQueue.Main.async

Difference between DispatchQueue types in swift

由 こ雲淡風輕ζ 提交于 2019-12-04 19:41:07
As I understand there are 3 types of DispatchQueue in swift: Main (serial) (Main Thread) Global (Concurrent) (Background Threads working in parallel) Custom (Concurrent or serial) And each one maybe work (asynch or synch) First question: Is it main queue working on UI thread only and not working on another thread? If the answer yes , how DispatchQueue.Main.async not blocking UI thread. If the answer No , what is the benefit of using DispatchQueue.global as long as DispatchQueue.Main.async work in another thread. Second question: what is deference between DispatchQueue.global (async) and

Applying filter to real time camera preview - Swift

由 孤街浪徒 提交于 2019-12-04 14:05:56
问题 I'm trying to follow the answer given here: https://stackoverflow.com/a/32381052/8422218 to create an app which uses the back facing camera and adds a filter, then displays it on the screen in real time here is my code: // // ViewController.swift // CameraFilter // import UIKit import AVFoundation class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate { var captureSession = AVCaptureSession() var backCamera: AVCaptureDevice? var frontCamera: AVCaptureDevice? var

Swift Async With Completion Block

由 浪子不回头ぞ 提交于 2019-12-03 22:32:57
问题 I have two functions that executes async. I tried to "syncronize" them with: DispatchGroup and DispatchQueue let queue = DispatchQueue(label: "com.company.app.queue", attributes: .concurrent) let group = DispatchGroup() queue.async(group: group) { //func1 } queue.async(group: group) { //func2 } group.notify(queue: queue) { print("#3 finished") } Func1 and Func2 are only calls of: class func getDataFromUrl( url: URL, completion: @escaping ( Data?, URLResponse?, Error? ) -> ( ) ) { URLSession

Applying filter to real time camera preview - Swift

由 隐身守侯 提交于 2019-12-03 08:46:19
I'm trying to follow the answer given here: https://stackoverflow.com/a/32381052/8422218 to create an app which uses the back facing camera and adds a filter, then displays it on the screen in real time here is my code: // // ViewController.swift // CameraFilter // import UIKit import AVFoundation class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate { var captureSession = AVCaptureSession() var backCamera: AVCaptureDevice? var frontCamera: AVCaptureDevice? var currentCamera: AVCaptureDevice? var photoOutput: AVCapturePhotoOutput? var cameraPreviewLayer:
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