How do I dispatch sync dispatch async dispatch after etc in Swift 3 Swift 4 and beyond

Question

I have lots of code in Swift 2 x  or even 1 x  projects that looks like this      Move to a background thread to do some long running work dispatch async dispatch get global queue DISPATCH QUEUE PRIORITY DEFAULT  0         let image   self loadOrGenerateAnImage          Bounce back to the main thread to update the UI     dispatch async dispatch get main queue              self imageView image   image           Or stuff like this to delay execution   dispatch after dispatch time DISPATCH TIME NOW  Int64 0 5   Double NSEC PER SEC     dispatch get main queue          print  test       Or any of all kinds of other uses of the Grand Central Dispatch API     Now that I ve opened my project in Xcode 8  beta  for Swift 3  I get all kinds of errors  Some of them offer to fix my code  but not all of the fixes produce working code  What do I do about this

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in Xcode 8 use   DispatchQueue global qos   userInitiated  async

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In Xcode 8 beta 4 does not work     Use   DispatchQueue main asyncAfter deadline   now     0 5        print  Are we there yet        for async two ways   DispatchQueue main async       print  Async1      DispatchQueue main async  execute        print  Async2

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This one is good example for Swift 4 about async   DispatchQueue global qos   background  async          Background Thread     DispatchQueue main async              Run UI Updates or call completion block

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Since the beginning  Swift has provided some facilities for making ObjC and C more Swifty  adding more with each version  Now  in Swift 3  the new  import as member  feature lets frameworks with certain styles of C API -- where you have a data type that works sort of like a class  and a bunch of global functions to work with it -- act more like Swift-native APIs  The data types import as Swift classes  their related global functions import as methods and properties on those classes  and some related things like sets of constants can become subtypes where appropriate   In Xcode 8   Swift 3 beta  Apple has applied this feature  along with a few others  to make the Dispatch framework much more Swifty   And Core Graphics  too   If you ve been following the Swift open-source efforts  this isn t news  but now is the first time it s part of Xcode   Your first step on moving any project to Swift 3 should be to open it in Xcode 8 and choose Edit   Convert   To Current Swift Syntax    in the menu  This will apply  with your review and approval  all of the changes at once needed for all the renamed APIs and other changes   Often  a line of code is affected by more than one of these changes at once  so responding to error fix-its individually might not handle everything right    The result is that the common pattern for bouncing work to the background and back now looks like this      Move to a background thread to do some long running work DispatchQueue global qos   userInitiated  async       let image   self loadOrGenerateAnImage          Bounce back to the main thread to update the UI     DispatchQueue main async           self imageView image   image           Note we re using  userInitiated instead of one of the old DISPATCH QUEUE PRIORITY constants  Quality of Service  QoS  specifiers were introduced in OS X 10 10   iOS 8 0  providing a clearer way for the system to prioritize work and deprecating the old priority specifiers  See Apple s docs on background work and energy efficiency for details   By the way  if you re keeping your own queues to organize work  the way to get one now looks like this  notice that DispatchQueueAttributes is an OptionSet  so you use collection-style literals to combine options    class Foo        let queue   DispatchQueue label   com example my-serial-queue                              attributes    serial   qosUtility       func doStuff             queue async               print  Hello World                       Using dispatch after to do work later  That s a method on queues  too  and it takes a DispatchTime  which has operators for various numeric types so you can just add whole or fractional seconds   DispatchQueue main asyncAfter deadline   now     0 5       in half a second        print  Are we there yet        You can find your way around the new Dispatch API by opening its interface in Xcode 8 -- use Open Quickly to find the Dispatch module  or put a symbol  like DispatchQueue  in your Swift project playground and command-click it  then brouse around the module from there   You can find the Swift Dispatch API in Apple s spiffy new API Reference website and in-Xcode doc viewer  but it looks like the doc content from the C version hasn t moved into it just yet    See the Migration Guide for more tips

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Swift 4 1 and 5  We use queues in many places in our code  So  I created Threads class with all queues  If you don t want to use Threads class you can copy the desired queue code from class methods   class Threads      static let concurrentQueue   DispatchQueue label   AppNameConcurrentQueue   attributes   concurrent    static let serialQueue   DispatchQueue label   AppNameSerialQueue         Main Queue   class func performTaskInMainQueue task   escaping   - gt           DispatchQueue main async         task                   Background Queue   class func performTaskInBackground task  escaping    throws - gt            DispatchQueue global qos   background  async         do           try task           catch let error as NSError           print  error in background thread   error localizedDescription                            Concurrent Queue   class func perfromTaskInConcurrentQueue task  escaping    throws - gt            concurrentQueue async         do           try task           catch let error as NSError           print  error in Concurrent Queue   error localizedDescription                            Serial Queue   class func perfromTaskInSerialQueue task  escaping    throws - gt            serialQueue async         do           try task           catch let error as NSError           print  error in Serial Queue   error localizedDescription                            Perform task afterDelay   class func performTaskAfterDealy   timeInteval  TimeInterval    task  escaping    - gt            DispatchQueue main asyncAfter deadline    now     timeInteval           task                 Example showing the use of main queue   override func viewDidLoad         super viewDidLoad        Threads performTaskInMainQueue             Update UI

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Swift 5 2  4 and later  Main and Background Queues   let main   DispatchQueue main let background   DispatchQueue global   let helper   DispatchQueue label   another thread      Working with async and sync threads    background async     async tasks here     background sync     sync tasks here      Async threads will work along with the main thread   Sync threads will block the main thread while executing

[swift] How do I dispatch_sync, dispatch_async, dispatch_after, etc in Swift 3, Swift 4, and beyond?

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