Dispatchqueue Main Async Time

cs will be run, before your application is shown on screen. Use SynchronizationContext and ConfigureAwait for this. This call pattern is useful when you want to have the calling thread do work at the same time that the asynchronous call is executing. DispatchQueue. 由于在项目中需要用到定时关闭功能音频功能,本来打算用NSTimer的,可是写起来并不是那么精简好用,所以又在网上找到相关的实例,结合自己项目需要,就写出了如下代码,还请大家指教,废话不多说:impor. Explicitly switch to the UI thread in an async method. Async operations like promises are put into an event queue, which runs after the main thread has finished processing so that they do not block subsequent JavaScript code from running. 5, async is used to declare a function as a coroutine, much like what the @asyncio. I finally got the time to write after a few months of being really busy. global() に. From here on, it's getting the version stable for its release. One most important thing to learn when developing for the iOS platform is to never block the main thread. 👉 This article has been updated and republished, read the latest version here NodeJS supports async/await out of the box since version 7. If we create a big pool under heavy io pressure, it's easy to let osd down/in because of heartbeat message blocking. Thus, an asynchronous function does not block the current thread of execution from proceeding on to the next function. coroutine decorator does. Hi there! This is a complete guide that will help you to master networking in Swift. async {} 即可,也就是说,大概是这样: DispatchQueue. UI updates should only happen on the main thread, which just happens to be a serial queue. sync will queue up the closure block on the queue. 現在、DispatchQueueについて悩んでいます。 下記のコードをswift3. OK, I Understand. By continuing to use Pastebin, you agree to our use of cookies as described in the Cookies Policy. DispatchQueue. Currently, there is certainly a little lag the first time it runs to get these files. For example, the following snippet of code (requires Python 3. Sync threads will block the main thread while executing. How to create dispatch queue in Swift 3 DispatchQueue. DispatchQueue. The Asynchronous Design approach, as you may already be familiar with deals with functions that are used to initiate tasks that take time to complete, during which the control is transferred back without having to wait for the function to execute. 第二种是作为参数传给async方法。 DispatchQueue. DispatchQueue has a version of async that takes a qos as an argument. Theo, the Swift framework for interfacing with Neo4j, is now available in version 3. When user runs app, the system automatically creates a serial dispatch queue which runs app’s main thread. Synchronous and asynchronous are confusing concepts in JavaScript, especially for beginners. In part, this resembles DispatchQueue, where the caller can run work on the queue using sync or async. A discussion about how to use asynchronous techniques in HTML5. So I was working on this FlickrKit a while back and at that time I decided to write about it, on how to use it with Swift. sync { //Stuff Here } using Swift 3 To get one of the background threads. You made a singleton thread safe for reading and writing using a combination of dispatch barriers and synchronous. io is a third-party service which tracks SDKs usage in the top iOS + Android apps. The async method is on pause until the awaitable is complete (wait), but the thread is not blocked by this call (it is asynchronous). 1)mainは何を意味するのでしょうか?. Another reason for my interest in asynchronous processing has to do with (perceived) performance. Promises are an alternative to callbacks for delivering the results of an asynchronous computation. async { //async tasks here } background. They are a number of ways to solve this, depending upon your. In this program we define a function called print to be called when the asynchronous wait finishes. NET controls, including custom controls and DataSources, when the controls are on async pages. We can easily implement Asynchronous using 'async' and 'await' keywords. Using Async and Await to update the UI Thread October 14, 2014 October 17, 2014 Stephen Haunts 5 Comments In a previous article on async and await , I showed a very simple example of how to run some code asynchronously. ‘DispatchQueue. For almost every function there exist two variants, one that locks the queue and one that doesn't. More than 1 year has passed since last update. 再使用 DispatchQueue. 同样的,你不需要在去用 dispatch_get_main_queue() 来获取主线程,而是 DispatchQueue. On my use I had to use DispatchQueue. timeIntensiveTask() } } The task got executed instantly after I pressed the IBAction, and took about 5 seconds to complete. With just one attribute, by decorating the @Page directive with Async='true', developers can spawn one or more long-running operations, returning the main thread to ASP. hpp > Using asio's asynchronous functionality means having a callback function that will be called when an asynchronous operation completes. The new async/await asynchronous programming facilities in. Get #Buildspiration with Asynchronous Apex Triggers in Summer '19. You can of course customize this. main let background = DispatchQueue it runs at the same time with the main queue. The difference between running the method in a thread and having the method be an async thread is that an async method waits until the first await statement to return to the main thread for processing whereas threading the method immediately continues to the next statement in the main method. So, the Rust's async-await is an area of interest for me. main (that is, action 2 only happens after action 1 ends), while the contents of DispatchQueue. let serialQueue = DispatchQueue(label: "queuename") serialQueue. DispatchQueue(IntPtr) Surfaces an unmanaged DispatchQueue as a managed object. global(qos:. Currently, there is certainly a little lag the first time it runs to get these files. According to Meloni (2010) asynchronous communication and learning is by far the more popular learning type because many of the learning tools are free. Run(() => SomeStuff()) is not even the main point of async, it's just an easy example for people who are used to typing ThreadPool. Two or more things are synchronous when they happen at the same time (in sync), and asynchronous when they don't (not in sync). Simple to use: DispatchQueue. swift 3中对C层级的GCD的API进行了彻头彻尾的改变。达内ios培训(ios. after 让这个操作在 60 秒后执行。 相比于之前的 GCD 语法,那就容易理解很多了。 顺手儿把 GCD 以前获取当前时间的语法贴出来对比一下: let dispatch_time = dispatch_time(DISPATCH_TIME_NOW, Int64 (60 * NSEC_PER_SEC)) 这样一比, 立竿见影哈。. In fact all the methods in a method chain should be made awaitable except the method which is called from the main method. In the world of iOS software development, its imperative that we make the experience of using apps as seamless as. This command means - do other stuff that are between these two lines of code, without locking the main thread, and once SlowDude is finished proceed further. Async rabbit consumer is useful when your consumer's event handler needs to do async stuff (e. A new Thread()is not dealing with Thread pool thread, whereas Task does use thread pool thread. async { //async tasks here } background. async { self. async 使用主线程更新相应的 UI 内容。. Coroutines declared with async/await syntax is the preferred way of writing asyncio applications. 在ios的开发和学习中多线程编程是必须会遇到并用到的。 在 java 中以及Android开发中,大量的后台运行,异步消息队列,基本都是运用了多线程来实现。. Having async keyword before def, with and for also makes the language grammar simpler. async { // Run async code on the main queue} But it turns out that if we dive a little bit deeper, GCD also has a suite of really powerful APIs and features that not everyone knows about. Simply put - annotating a method of a bean with @Async will make it execute in a separate thread i. AWS Lambda Function Handler in C#. dispatch_async. The websocket code is running on a background thread. async { //Stuff Here } How to use Swift 3 to Get the main queue Synchronously: DispatchQueue. background ). However, asynchronous programming is not that easy as it seems with the support provided in programming languages like C# and Java. Apple disclaims any and all liability for the acts, omissions and conduct of any third parties in connection with or related to your use of the site. Asynchronous JavaScript is a fairly advanced topic, and you are advised to work through JavaScript first steps and JavaScript building blocks modules before attempting this. DispatchQueue. Sleep in the above way, there is nothing you can do to abort this except waiting until the time elapses or by restarting the application. You can't make a lambda that returns a value async. En d’autres termes, je veux que mon application exécute le code, mais à un moment donné, faites une pause de 4 secondes, puis continuez avec le rest du code. The syntax part of the chaining works by having class methods on the Async object e. main, which is the main thread, rather than one of the global quality of service queues. DispatchQueue. To use the canonical example, downloading a web page, we can write code for downloading a web page. async { //async tasks here } background. You can also tune the Executor to increase the corePoolSize attribute for instance. For standardized barcodes such as SEPA payment barcode, PDF417 also features parsing. after 让这个操作在 60 秒后执行。 相比于之前的 GCD 语法,那就容易理解很多了。 顺手儿把 GCD 以前获取当前时间的语法贴出来对比一下: let dispatch_time = dispatch_time(DISPATCH_TIME_NOW, Int64 (60 * NSEC_PER_SEC)) 这样一比, 立竿见影哈。. DispatchQueue(IntPtr) Surfaces an unmanaged DispatchQueue as a managed object. 1 Overview #. global(attributes:. To compare how long this takes without the asynchronous feature, try commenting out the @Async annotation and runing the service again. The execution time of the I/O selector is logged if it takes too long to perform an I/O operation. A certain event would always follow another and they can't be interchanged. This method will suspend the current thread until the given amount of time has elapsed. Yet NServiceBus hasn't been exposing asynchronous. swift 3中对C层级的GCD的API进行了彻头彻尾的改变。达内ios培训(ios. Grand Central Dispatch (GCD) and Dispatch Queues in Swift 3. sync [duplicate] Posted by: admin February 24, As well as global or private at the same time. Async Resources. 0 app so I'm just getting to grips with Tasks and async/await & wanted to confirm I was using it in the correct way. C# Async Tips & Tricks 04 October 2017 on async, csharp, c#. If you don't call from Main, Runtime could call back on any thread. In asynchronous code flows, it is commonplace to execute two or more tasks concurrently. managedObjectContext. In asynchronous sequential circuits the inputs are levels and there are no clock pulses; the inputs events drive the circuit. Reading the last value is not optimized because multiple read requests have to wait for each other as it is in a serial queue. ) New in Xcode 9 and enabled by default is the Main Thread Checker (Product > Scheme > Edit Scheme > Diagnostics > Runtime API Checking > Main Thread Checker). And "async def" better separates coroutines from regular functions visually. 一次性执行(dispatch_once_t)实际开发中有时我们需要某个方法只执行一次,而且要保证线程是安全的,那么dispatch_once_t无疑是很好的选择。. 你确实可以调用等待两次来概念性地获取资源两次. notify(queue: DispatchQueue. 其实这个标题不知道怎么写了,都很碎,也没有想到特别合适的例子能够全部放在一起的。索性就这么平铺开吧。 使用dispatch_once函数能保证某段. That's where asynchronous JavaScript comes into play. async { [weak self] in your code runs in main thread} 优先级. Today, we'll be learning how to use AV Foundation, an Apple system framework that exists on macOS and iOS, along with watchOS and tvOS. 기존의 NSThread, NSOperation보다 보다 쉽게 처리가 가능하다는 장점이 있을듯. main { // to do something }. The "async" keyword enables the "await" keyword in that method and changes how method results are handled. 1)mainは何を意味するのでしょうか?. Having async keyword before def, with and for also makes the language grammar simpler. 7+) prints "hello", waits 1 second, and then prints "world":. Recently, I was involved in a thread on Stack Overflow discussing the proper usage of weak references and it occurred to me that since I see so much discussion about this topic it would be good to write a post detailing my understanding on the usage of weak references. 版权声明:本文内容由互联网用户自发贡献,版权归作者所有,本社区不拥有所有权,也不承担相关法律责任。. async { //async tasks here } background. global() let helper = DispatchQueue(label:"another_thread") 使用异步和同步线程 ! background. Introduced in Python 3. In iOS or OSX threads categorized into two as below: Main Thread (UI Thread) Background Thread; Main Thread. So if you do have a need to mix Objective-C and Swift async code, promises looks like a pretty good option to consider! However, these benchmarking comparisons aren’t going to mean very much in typical usage patterns, so you should probably go with whatever syntax feels most collegial, really. They require more effort from implementors of asynchronous functions, but provide several benefits for users of those functions. notifyQueue에서 mainQueue를 꼭 사용할 필요 없이 큐를 별도로. The websocket code is running on a background thread. async around two of my other functions that related to the UI as apparently that was needed (was getting purple errors telling me they had to be run on the main thread) but now functionally it all works perfectly. Initially, a document-based application has a method called analyzeDocument which may do something like count the number of words and paragraphs in the document. static getnthPrime(SendPort sendPort) async {At this point, we have set up the send port of the main isolates to the prime isolate. In this video we will discuss async and await keywords and their use with an example. I feel that there is a general problem with throwing an exception on UI thread, but at the same time I don't understand why catch block isn't saving me from exception. The key to the solution is to keep a weak reference in an array, indexed by the objectID of the observer in the observable. async {} inside the blockOperation to run my code because it was an autolayout animation. What are the differences between. The struct has matching methods e. dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(3. These statistics consist of (i) the elapsed real time between invocation and termination, (ii) the user CPU time (the sum of the tms_utime and tms_cutime values in a struct tms as returned by times(2)), and (iii) the system CPU time (the sum of the tms_stime and tms_cstime values in a struct tms as returned by times(2)). We will use async await for building fully asynchronous Web API. Grand Central Dispatch (GCD) and Dispatch Queues in Swift 3. Use SynchronizationContext and ConfigureAwait for this. GCD provides three main types of queues: Main queue: runs on the main thread and is a serial queue. For every request, the API Hits count increases. Building the future of event-driven architectures. 0 is feature complete. That is to say: code that executes one operation at a time. Thus, switching power to stator windings at the right time causes a flux pattern that results in either clockwise or counterclockwise motion. Calling Runtime from the main thread is a pretty good indicator that you're calling because of a user interaction, so it's reasonable to expect that you'd want to update some UI when Runtime responds (and that always needs to happen on the main thread). If any of the tasks takes a lot of time, things will be bad. The async attribute is a boolean attribute. global() returns a concurrent queue, which can be backed by hundreds of threads of execution. async 相当于使用全局队列进行异步操作。然后在调用 DispatchQueue. 同样的,你不需要在去用 dispatch_get_main_queue() 来获取主线程,而是 DispatchQueue. Async methods are intended to be non-blocking operations. delegate as YourAppDelegateClass delegateObj. DispatchQueue. 在ios的开发和学习中多线程编程是必须会遇到并用到的。 在 java 中以及Android开发中,大量的后台运行,异步消息队列,基本都是运用了多线程来实现。. While it's not necessary that you learn all these concepts to be an awesome JavaScript developer, it's helpful to know :). If you need to update the GUI, please change the dispatch mechanism to publish on the main thread. by Paul Breslin How to write beautiful Node. This could be accomplished by either setting the dispatchQueue property of the capture instance to DispatchQueue. global(qos:) will concurrently (everything at the same time) run into background thread(s) (if there are several actions) with priority equal to the priority of the selected QoS. Thus, an asynchronous function does not block the current thread of execution from proceeding on to the next function. Notify(DispatchQueue, Action) Schedule a block to be submitted to a queue when all the blocks associated with a group have completed. We can easily implement Asynchronous using 'async' and 'await' keywords. All I did was to put a delay in Main after calling the async method, the metod gets called asynchornously, the main thread does not wait and contiunes to execute the delay loop and finally I see the file being created and written to. Welcome to the second and final part of this Grand Central Dispatch tutorial series! In the first part of this series, you learned about concurrency, threading, and how GCD works. NET solve one of its long standing problems - how to write and an elegant application that uses the UI correctly. A lightweight Swift library & syntactic sugar for async (GCD) operations - chryb/coex. What is happening when doTheJob is called and you dispatch to the main queue, is you're saying, queue up this block of code to run on the main thread, the call to start animation. Topic archived. There are, however, three big hints that this is the right thing to do: Apple’s documentation says “It’s expected that the widget will perform the work to update asynchronously and off the main thread as much as. They make your asynchronous code less "clever" and more readable. The asynchronous callback programming model has many benefits; you can depend on asynchronous callback methods to perform expensive I/O while your processor is busy executing some other task. 你确实可以调用等待两次来概念性地获取资源两次. Except for the dispatch queue representing your app's main thread, the system makes no guarantees about which thread it uses to execute a task. With asynchronous code, that is an entirely different story. js, jQuery) in advance. It also improves the utilization and quality of service (QoS) of high-traffic networks. Normally you perform a dispatch_async on the main thread and then let your background thread run. managedObjectContext. Here Iam doing task to save data in. So I think I should use a task and await it when I want to wait, and not await it when I don't want to wait. In this example, we create an asynchronous version of a method that processes a list of files. Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by ANSI and ITU (formerly CCITT) standards for carriage of user traffic, including telephony (voice), data, and video signals. Notify(DispatchQueue, Action) Schedule a block to be submitted to a queue when all the blocks associated with a group have completed. 1 Overview #. async { // Some code that takes a long time to execute } Run code on the main thread from a background thread. Asynchronous learning is a student-centered teaching method that uses online learning resources to facilitate information sharing outside the constraints of time and place among a network of people. Parameters rel_time The time span after which the function returns resuming execution of the calling thread. After swift 3. We can fulfil the expectation in a callback. This is really handy for doing things like quickly adding images. get also has a variant that waits for a given amount of time. That is to say: code that executes one operation at a time. 0 (dispatch_async was replaced with DispatchQueue. NET solve one of its long standing problems - how to write and an elegant application that uses the UI correctly. dispatch_async. The async method is on pause until the awaitable is complete (wait), but the thread is not blocked by this call (it is asynchronous). But that doesn't significantly increase the load time. DispatchQueue(String, Boolean) Creates a named dispatch queue that can optionally execute any submitted code concurrently. Simply put - annotating a method of a bean with @Async will make it execute in a separate thread i. The async attribute is a boolean attribute. main, which is the main thread, rather than one of the global quality of service queues. after 让这个操作在 60 秒后执行。 相比于之前的 GCD 语法,那就容易理解很多了。 顺手儿把 GCD 以前获取当前时间的语法贴出来对比一下: let dispatch_time = dispatch_time(DISPATCH_TIME_NOW, Int64(60 * NSEC_PER_SEC)). async { self. A thread which design to execute all AppKit, UIKit and other standard UI API and code. Normally you perform a dispatch_async on the main thread and then let your background thread run. Using Async and Await to update the UI Thread October 14, 2014 October 17, 2014 Stephen Haunts 5 Comments In a previous article on async and await , I showed a very simple example of how to run some code asynchronously. Note that EndInvoke() does not return until the asynchronous call has completed. Building the future of event-driven architectures. printApples() } mainQueue. The async and await keywords have been a part of C# language since version 5. Asynchronous applications are typically easier to scale, allow for the implementation of reliability patterns and sometimes better reflect use cases in the real world. async and DispatchQueue. Main dispatch queue. The Async Upload Pipeline has the following process for each command:. global(qos:. From here on, it's getting the version stable for its release. If you google the meaning of the words you will get the following: Asynchronous: not existing or occurring at the Stack Exchange Network Stack Exchange network consists of 175 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Instabug helps mobile teams connect with customers, to iterate faster, and to release with a higher degree of confidence. The async method is on pause until the awaitable is complete (wait), but the thread is not blocked by this call (it is asynchronous). DispatchQueue. More than 1 year has passed since last update. 1 and waiting it out to see how everything develops. In iOS or OSX threads categorized into two as below: Main Thread (UI Thread) Background Thread; Main Thread. global() システムにより予め生成されている5つのDispatchQueueを参照します。 5つのDispatchQueueは、DispatchQueue. main’ means you want to call the code inside block ‘{}’ on main thread. async { // call UI functions with the results of the above } }. public void Notify (CoreFoundation. To access in the code: let mainQueue = DispatchQueue. 4 comments on"How NOT to schedule repeating background tasks in Swift" SonnyWerghis April 05, 2017 So, what does this mean – that if you use a global queue, you run the risk that your code could affect the performance of another queue?. global(qos:. main as the delegate queue. setting the. Asynchronous UI Updating with the Main Queue. You have to be careful, because in a block you can easily create a retain-cycle, so you have to pass around your variables as weak or unowned references. let main = DispatchQueue. Recreating dynamic components is normally useful behavior, but in this case, we'd really like those tab component instances to be cached once they're created for the first time. printStrawberries() } mainQueue. Synchronous vs Asynchronous. Apple disclaims any and all liability for the acts, omissions and conduct of any third parties in connection with or related to your use of the site. 线程安全定义: 当多个线程访问一个类时,如果不用考虑这些线程在运行时环境下的调度和交替执行,并且不需要额外的同步及在调用方代码不必做其他的协调,这个类的行为仍然是正确的. You can also tune the Executor to increase the corePoolSize attribute for instance. Since we’re fetching using a private context, the completion closure will be executed in a background queue. DispatchQueue. async 相当于使用全局队列进行异步操作。然后在调用 DispatchQueue. NET to be used for other requests. 6 - for example, there's async with for asynchronous context managers, and async for for asynchronous iterators - but they require the objects you're using them on to have provided asynchronous implementations of those operations (like defining an __aiter__ method). For our implementation, in principal, it requires to hand over a callback to the asynchronous method, that in turn will invoke the callback. dispatch_once,以及Swift下的单例 使用dispatch_once函数能保证某段代码在程序运行过程中只被执行1次。. let main = DispatchQueue. This style of system design has been prevalent for a long time at the operating system level. The order would still be the same in this example. , CorrelationManager for TraceSource, or the Nested Diagnostic Context for log4net). Remember, the await keyword is only valid inside async functions. dylib) [0x7fff89cd29ee] 51 kevent + 10 (libsystem_kernel. The queued operations will complete as soon as possible then return their results to the JavaScript environment. io is a third-party service which tracks SDKs usage in the top iOS + Android apps. Ah, I forgot to mention that in my initial reply. 线程安全定义: 当多个线程访问一个类时,如果不用考虑这些线程在运行时环境下的调度和交替执行,并且不需要额外的同步及在调用方代码不必做其他的协调,这个类的行为仍然是正确的. UI updates should only happen on the main thread, which just happens to be a serial queue. Note, the above syntax of adding seconds as a Double seems to be a source of confusion (esp since we were accustomed to adding nsec). It does parallelize it but in my example this would drop the load time from 2. The main dispatch queue is a globally available serial queue that executes tasks on the application's main thread. qosUserInitiated). 0 * Double(NSEC_PER_SEC))), dispatch_get_main_queue()) {} ```. image on a UIImageView), you need to be on the main thread. IO Module Module1 Sub Main() ' Create a Task with AddressOf. We can fulfil the expectation in a callback. NET solve one of its long standing problems - how to write and an elegant application that uses the UI correctly. Async Await Support in TypeScript. This is how I've come to remember the difference between synchronous and asynchronous messages:. 001s 51 _dispatch_mgr_thread + 54 (libdispatch. Async Resources. loadOrGenerateAnImage() // Bounce back to the main thread to update the UI DispatchQueue. async 相当于使用全局队列进行异步操作。然后在调用 DispatchQueue. Many things happen at once. The Asynchronous Design approach, as you may already be familiar with deals with functions that are used to initiate tasks that take time to complete, during which the control is transferred back without having to wait for the function to execute. To speed up the execution of multiple tasks, it makes sense to split the work over multiple threads, each performing a smaller task. When starting to work with testing (both unit testing and UI testing), one thing that every single developer starts encountering at some point is flakiness. The most common use case is for logging, where you can maintain a stack of logical operations so every time you log you capture (and log) the state of that stack (e. DispatchQueue. A event of sorts is set up that will signal that the asynchronous non-CPU-bound operation has completed/is ready, at which time the main thread will continue execution of the continuation that was set up earlier. async around two of my other functions that related to the UI as apparently that was needed (was getting purple errors telling me they had to be run on the main thread) but now functionally it all works perfectly. global() let helper = DispatchQueue(label:"another_thread") 使用异步和同步线程 ! background. With just one attribute, by decorating the @Page directive with Async='true', developers can spawn one or more long-running operations, returning the main thread to ASP. 一次性执行(dispatch_once_t)实际开发中有时我们需要某个方法只执行一次,而且要保证线程是安全的,那么dispatch_once_t无疑是很好的选择。. This codelab teaches you how to write asynchronous code using futures and the async and await keywords. async at the end to remove the voices loading message and replace it with the custom voice selector control, and also to initialize the sequencer which unhides the UISegmentedControl that allows you to record and play sequences. Maybe some don't like that it's rather "magical," hiding what's really going on from the programmer, but modern applications often follow a pattern falling exactly in line with what the async/await syntax is made for. Great work! Great work! - Quaggie Jan 9 at 12:58. Remember, the await keyword is only valid inside async functions. Augmented reality (AR) and machine learning are the hottest technologies on the market right now, so what we are going to build this time is a face recognition app that identifies people in our office and shows basic information when the app identifies someone who has been registered. The template function async runs the function f asynchronously (potentially in a separate thread which may be part of a thread pool) and returns a std::future that will eventually hold the result of that function call. More than 1 year has passed since last update. sync { //Stuff Here } using Swift 3 To get one of the background threads. In addition, on iOS, we also have a DispatchQueue sync context, so by default if you start an await call on a Grand Central Dispatch queue, then execution is resumed on that queue. These statistics consist of (i) the elapsed real time between invocation and termination, (ii) the user CPU time (the sum of the tms_utime and tms_cutime values in a struct tms as returned by times(2)), and (iii) the system CPU time (the sum of the tms_stime and tms_cstime values in a struct tms as returned by times(2)). DispatchQueue. To use the canonical example, downloading a web page, we can write code for downloading a web page. async { By default. global() let helper = DispatchQueue(label: "another_thread") Travailler avec des threads asynchrones et synchronisés! background. Thread 0x2fe7 DispatchQueue 1 73 samples (1-73) priority 46 48. main let background = DispatchQueue. Welcome to the second and final part of this Grand Central Dispatch tutorial series! In the first part of this series, you learned about concurrency, threading, and how GCD works. Dispatch queues execute tasks either serially or concurrently. Introduction. async { // Some code that takes a long time to execute } Run code on the main thread from a background thread.