Swift 3

   DispatchQueue.main.async {
        // Write your code here
    }

 DispatchQueue.main.async {
          self.collectionView?.reloadData() // Depends if you were populating a collection view or table view
    }


OperationQueue.main.addOperation {
    self.lblGenre.text = self.movGenre
}

//使用操作队列如果你需要填充对象(标签，imageview, textview)在你的视图控制器

DispatchQueue.main.async(execute: {
   // code
})

现在很简单:

let serialQueue = DispatchQueue(label: "my serial queue")

默认值是serial，要获得concurrent，可以使用可选属性参数.concurrent

在XCode 8编译，Swift 3 https://github.com/rpthomas/Jedisware

 @IBAction func tap(_ sender: AnyObject) {

    let thisEmail = "emailaddress.com"
    let thisPassword = "myPassword" 

    DispatchQueue.global(qos: .background).async {

        // Validate user input

        let result = self.validate(thisEmail, password: thisPassword)

        // Go back to the main thread to update the UI
        DispatchQueue.main.async {
            if !result
            {
                self.displayFailureAlert()
            }

        }
    }

}

 let newQueue = DispatchQueue(label: "newname")
 newQueue.sync { 

 // your code

 }