类变量分配在Alamofire请求块内不起作用

Question

I am trying to assign a Alamofire request result to a TableView class variable.

I have realized that when I use the self.notifications variable within Alamofire request block, it works. But when I call self.notifications outside of Alamofire it is nil and self.notifications is not be assigned by reference. It seems like a copy variable

class NotificationsTableView: UITableViewController{

    var notifications: Notification!
    let uri = Helper.URLDEV + "/api_x/notifications/"
    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.cellLayoutMarginsFollowReadableWidth = true
        self.tableView.delegate = self
        self.tableView.dataSource = self
        print("Table loaded")
        let auth_code = ["Authorization": "Token " + Helper.getMyToken() ]
        Alamofire.request(self.uri, parameters: nil, encoding: URLEncoding.default, headers: auth_code).responseJSON { response in
            guard let data = response.data else { return }
            do {
                let decoder = JSONDecoder()
                //This is working properly
                self.notifications = try decoder.decode(Notification.self, from: data)
                print(self.notifications?.results?[2].notificationData?.body ?? 999)

            } catch let error {
                print(error)
            }
        }
        print("URI: \(uri)")
        //Here is just nil, if I didn't assign a value before
        print(self.notifications == nil)

I expect self.notifications to not be nil after Alamofire request

Answer 1

The code in alamofire response will be executed when some response is received from the URL. Here the execution pointer is not going to wait for that response as it is a asynchronous call back and will continue to execute the next statement. So It will execute the statement outside the Alamofire first and as it is not initialised with any value, it will be nil and after some response is received some value is assigned to the class variable.

Below link will be able to get you through the async code

https://medium.com/ios-os-x-development/managing-async-code-in-swift-d7be44cae89f

Answer 2

最后，问题是使用Alamofire同步从此解决了回购 ，甚至与一个更干净的代码。