多用途螺纹功能

public enum QueueType {
        case Main
        case Background
        case LowPriority
        case HighPriority

        var queue: DispatchQueue {
            switch self {
            case .Main:
                return DispatchQueue.main
            case .Background:
                return DispatchQueue(label: "com.app.queue",
                                     qos: .background,
                                     target: nil)
            case .LowPriority:
                return DispatchQueue.global(qos: .userInitiated)
            case .HighPriority:
                return DispatchQueue.global(qos: .userInitiated)
            }
        }
    }

    func performOn(_ queueType: QueueType, closure: @escaping () -> Void) {
        queueType.queue.async(execute: closure)
    }

像这样使用它:

performOn(.Background) {
    //Code
}

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)
     }
}

好的答案，无论如何，我想分享我的面向对象的解决方案，直到swift 5。

请查看它:AsyncTask

从概念上受到android的AsyncTask的启发，我用Swift写了自己的类

AsyncTask允许正确和简单地使用UI线程。该类允许执行后台操作并在UI线程上发布结果。

下面是一些用法示例

例1 -

AsyncTask(backgroundTask: {(p:String)->Void in//set BGParam to String and BGResult to Void
        print(p);//print the value in background thread
    }).execute("Hello async");//execute with value 'Hello async'

例2 -

let task2=AsyncTask(beforeTask: {
           print("pre execution");//print 'pre execution' before backgroundTask
        },backgroundTask:{(p:Int)->String in//set BGParam to Int & BGResult to String
            if p>0{//check if execution value is bigger than zero
               return "positive"//pass String "poitive" to afterTask
            }
            return "negative";//otherwise pass String "negative"
        }, afterTask: {(p:String) in
            print(p);//print background task result
    });
    task2.execute(1);//execute with value 1

它有两个泛型类型:

BGParam -执行时发送给任务的参数类型。 BGResult -后台计算结果的类型。 当你创建一个AsyncTask时，你可以将这些类型传递给任何你需要传入和传入后台任务的类型，但如果你不需要这些类型，你可以将其标记为未使用的，只需将其设置为:Void或使用更短的语法:()

当一个异步任务执行时，它经过3个步骤:

beforeTask:()->在任务执行之前在UI线程上调用的Void。 backgroundTask: (param:BGParam)->BGResult在后台线程立即调用 afterTask:(参数:BGResult)->在UI线程上调用后台任务结果的Void

Dan Beaulieu在swift5中给出了答案(从swift 3.0.1开始也可以工作)。

斯威夫特5.0.1

extension DispatchQueue {

    static func background(delay: Double = 0.0, background: (()->Void)? = nil, completion: (() -> Void)? = nil) {
        DispatchQueue.global(qos: .background).async {
            background?()
            if let completion = completion {
                DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: {
                    completion()
                })
            }
        }
    }

}

使用

DispatchQueue.background(delay: 3.0, background: {
    // do something in background
}, completion: {
    // when background job finishes, wait 3 seconds and do something in main thread
})

DispatchQueue.background(background: {
    // do something in background
}, completion:{
    // when background job finished, do something in main thread
})

DispatchQueue.background(delay: 3.0, completion:{
    // do something in main thread after 3 seconds
})

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

我真的很喜欢Dan Beaulieu的答案，但是它在Swift 2.2中不起作用，我认为我们可以避免那些讨厌的强制打开!

func backgroundThread(delay: Double = 0.0, background: (() -> Void)? = nil, completion: (() -> Void)? = nil) {

    dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)) {

        background?()

        if let completion = completion{
            let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)))
            dispatch_after(popTime, dispatch_get_main_queue()) {
                completion()
            }
        }
    }
}