ios - viewLoad 上的 Swift JSON 解析执行

Question

我目前正在努力解决我的 viewController 上的一个小问题。我已经存储了用户信息来保存用户的登录状态，无论如何，当用户打开应用程序时，他们会显示“个人资料”页面。我试图(在本例中返回电子邮件)在应用程序打开时返回与该用户相关的值，但不知道如何在 Controller 本身上执行代码，我的 JSON 发布在下面并返回正确的所需信息。但是，我的标签仍然无法获取用户打开应用程序时存储的电子邮件的值。标签保持空白!

    let myUrl = NSURL(string: "http://www.mywebsite.co.za/php/scripts/getuserEmail.php");
    let request = NSMutableURLRequest(URL:myUrl!);
    request.HTTPMethod = "POST";
    let postString = "user_id=\(userId)";
    request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding);
    let task = NSURLSession.sharedSession().dataTaskWithRequest(request)
        {
            data, response, error in
            println(" response = \(response)")
            let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)
            println("response data = \(responseString)")
            var err: NSError?
            var json = NSJSONSerialization.JSONObjectWithData(data, options: .MutableContainers, error: &err) as? NSDictionary
            if let parseJSON = json
            {
                var userEmail = parseJSON["userEmail"] as? String
                self.usersEmail.text = userEmail
            }
        }

基本上希望代码在该 View 打开时执行和更新我的标签，因为用户已经能够从另一个 View Controller 更改电子邮件，因此电子邮件应该相应更新。我们很乐意提供任何其他信息。

添加:在 myUrl 变量分配之后，控制台的 println 将不会执行。下面的回复仍然不起作用，但这是我在 viewWillAppear 上的完整代码:

 override func viewWillAppear(animated: Bool) {
    super.viewDidAppear(animated)

    let userFirstName = NSUserDefaults.standardUserDefaults().stringForKey("userFirstName")
    let userLastName = NSUserDefaults.standardUserDefaults().stringForKey("userLastName")
   var userFullName = userFirstName!

    userFullNameLabel.text = userFullName

    let userId:String? = NSUserDefaults.standardUserDefaults().stringForKey("userId")
    let imageUrl = NSURL(string:"http://www.mywebsite.co.za/profile-pictures/\(userId!)/user-profile.jpg")


    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
    let imageData = NSData(contentsOfURL: imageUrl!)

        if(imageData != nil )
        {
          dispatch_async(dispatch_get_main_queue(),{
            self.profilePictureImageVIew.image = UIImage(data: imageData!)
            self.profilePictureImageVIew.backgroundColor = UIColor.clearColor()
          })
        }
   }


    // Send HTTP POST
        let myUrl = NSURL(string: "http://www.mywebsite.co.za/php/scripts/getuserEmail.php");
        let request = NSMutableURLRequest(URL:myUrl!);
        request.HTTPMethod = "POST";
        let postString = "user_id=\(userId)";
        request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding);
        let task = NSURLSession.sharedSession().dataTaskWithRequest(request)
            {
                data, response, error in
                // You can print out response object
                println("******* response = \(response)")
                // Print out reponse body
                let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)
                println("****** response data = \(responseString)")
                var err: NSError?
                var json = NSJSONSerialization.JSONObjectWithData(data, options: .MutableContainers, error: &err) as? NSDictionary
                if let parseJSON = json
                {
                    var userEmail = parseJSON["userEmail"] as? String
                    self.usersEmail.text = userEmail
                }
        }
}

Answer 1

如果我理解正确，您的意思是页面已显示，但您对网络的调用尚未完成并分配给 self.usersEmail.text 。我在项目中所做的就是在主队列上异步分派(dispatch)像您这样的 block 中的命令。尝试在 if 语句中执行此操作:

dispatch_async(dispatch_get_main_queue()) {
    var userEmail = parseJSON["userEmail"] as? String
    self.usersEmail.text = userEmail
}

希望这有帮助。这可能不合适，但希望有人可以告诉我是否合适。到目前为止，它对我有用。

您还需要在其 block 之后恢复任务:

    let myUrl = NSURL(string: "http://www.mywebsite.co.za/php/scripts/getuserEmail.php");
    let request = NSMutableURLRequest(URL:myUrl!);
    request.HTTPMethod = "POST";
    let postString = "user_id=\(userId)";
    request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding);
    let task = NSURLSession.sharedSession().dataTaskWithRequest(request)
        {
            data, response, error in
            // You can print out response object
            println("******* response = \(response)")
            // Print out reponse body
            let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)
            println("****** response data = \(responseString)")
            var err: NSError?
            var json = NSJSONSerialization.JSONObjectWithData(data, options: .MutableContainers, error: &err) as? NSDictionary
            if let parseJSON = json
            {
                var userEmail = parseJSON["userEmail"] as? String
                self.usersEmail.text = userEmail
            }
    }
    task.resume()