Swift - 多线程开发

class Asyncs {
    
    public typealias Task = () -> Void

    private static func _async(_ task: @escaping Task,
                               _ mainTask: Task? = nil) {
        
        let item = DispatchWorkItem(block: task)
        DispatchQueue.global().async(execute: item)
        if let main = mainTask {
            item.notify(queue: DispatchQueue.main, execute: main)
        }
        
    }

    public static func async(_ task: @escaping Task){

        _async(task)
        
    }
    
    public static func async(_ task:@escaping Task,
                             _ mainTask:@escaping Task) {
        
        _async(task, mainTask)
        
    }
    
    
}

       Asyncs.async {
            print(Thread.current)
           // 子线程 <NSThread: 0x600003af5dc0>{number = 4, name = (null)}
        }
        Asyncs.async {
            print(Thread.current)
           // 子线程 <NSThread: 0x600003af37c0>{number = 6, name = (null)}
        } _: {
            print(Thread.current) 
            // 主线程 <_NSMainThread: 0x600003ab4940>{number = 1, name = main}
        }

打印

<NSThread: 0x600003af5dc0>{number = 4, name = (null)}
<NSThread: 0x600003af37c0>{number = 6, name = (null)}
<_NSMainThread: 0x600003ab4940>{number = 1, name = main}