GCD in Swift

在Objective-c 中的我们常用的GCD如何在Swift中使用呢？例如：dispatch_async,dispatch_after etc.

• Global

DispatchQueue.global(qos: .userInitiated).async {
 }

为何用.userInitiated 代替 DISPATCH_QUEUE_PRIORITY请参考苹果文档

• Main

 DispatchQueue.main.async {
        
  }

• After

DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { // in half a second...
    print("Are we there yet?")
}

• Custom

let queue = DispatchQueue(label: "com.zhuo.my-serial-queue",
                           attributes: [.serial, .qosUtility])
    func doStuff() {
        queue.async {
            print("Hello")
        }
    }

下载图片

DispatchQueue.global(qos: .userInitiated).async {
    let image = self.loadAnImage()
    // To the main thread to update the UI
    DispatchQueue.main.async {
        self.imageView.image = image
    }
}