在Swift 4.2中，这是可行的。

import Foundation

class myThread: Thread
{
    override func main() {
        while(true) {
            print("Running in the Thread");
            Thread.sleep(forTimeInterval: 4);
        }
    }
}

let t = myThread();
t.start();

while(true) {
    print("Main Loop");
    sleep(5);
}

在我们的iOS应用中，中央调度是用来处理多任务的。

您可以使用此代码

// Using time interval

DispatchQueue.main.asyncAfter(deadline: DispatchTime.now()+1) {
    print("Hello World")
}

// Background thread
queue.sync {
     for i in 0..<10 {
          print("Hello", i)
     }
}

// Main thread
for i in 20..<30 {
     print("Hello", i)
}

更多信息请访问这个链接:https://www.programminghub.us/2018/07/integrate-dispatcher-in-swift.html

dispatch_async(dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0), {
    // Conversion into base64 string
    self.uploadImageString =  uploadPhotoDataJPEG.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.EncodingEndLineWithCarriageReturn)
})

快4.倍

把这些放到文件中:

func background(work: @escaping () -> ()) {
    DispatchQueue.global(qos: .userInitiated).async {
        work()
    }
}

func main(work: @escaping () -> ()) {
    DispatchQueue.main.async {
        work()
    }
}

然后在需要的地方调用它:

background {
     //background job
     main {
       //update UI (or what you need to do in main thread)
     }
}

Swift 3版本

Swift 3利用新的DispatchQueue类来管理队列和线程。要在后台线程上运行一些东西，你可以使用:

let backgroundQueue = DispatchQueue(label: "com.app.queue", qos: .background)
backgroundQueue.async {
    print("Run on background thread")
}

或者如果你想在两行代码中实现:

DispatchQueue.global(qos: .background).async {
    print("Run on background thread")

    DispatchQueue.main.async {
        print("We finished that.")
        // only back on the main thread, may you access UI:
        label.text = "Done."
    }
}

你也可以在本教程中获得一些关于Swift 3中GDC的深入信息。

斯威夫特5

为了简化，创建一个“DispatchQueue+Extensions.swift”文件，内容如下:

import Foundation

typealias Dispatch = DispatchQueue

extension Dispatch {

    static func background(_ task: @escaping () -> ()) {
        Dispatch.global(qos: .background).async {
            task()
        }
    }

    static func main(_ task: @escaping () -> ()) {
        Dispatch.main.async {
            task()
        }
    }
}

用法:

Dispatch.background {
    // do stuff

    Dispatch.main { 
        // update UI
    }
}