Swift 3/iOS UIView not updating after retrieving remote JSON data - ios

Question

I have a UITableView with a list of users. When you tap on a row, the uid of the user is passed to the UIViewController detail view. A URLRequest is made to retrieve JSON data of the user (username, avatar, etc). However, the detail view inconsistently updates the information. Sometimes it'll show the users' name, avatar, etc but other times it'll show nothing or it'll only show the username or only show the avatar, etc.
In the fetchUser() method, I have a print("Username: \(self.user.username)") that shows the correct data is being retrieved 100% of the time but it won't display it 100% of the time in the view.
Any help would be greatly appreciated.
Thanks!
class ProfileViewController: UIViewController {
#IBOutlet weak var avatarImageView: UIImageView!
#IBOutlet weak var usernameLabel: UILabel!
#IBOutlet weak var networthLabel: UILabel!
var user: User!
var uid: Int?
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
fetchUser()
}
func reloadView() {
self.usernameLabel.text = user.username
self.networthLabel.text = "$" + NumberFormatter.localizedString(from: Int((user.networth)!)! as NSNumber, number: NumberFormatter.Style.decimal)
self.avatarImageView.downloadImage(from: user.avatar!)
circularImage(photoImageView: self.avatarImageView)
}
func fetchUser() {
// Post user data to server
let myUrl = NSURL(string: "http://localhost/test/profile")
let urlRequest = NSMutableURLRequest(url: myUrl! as URL);
urlRequest.httpMethod = "POST"
let postString = "uid=\(uid!)"
urlRequest.httpBody = postString.data(using: String.Encoding.utf8)
let task = URLSession.shared.dataTask(with: urlRequest as URLRequest) { (data, response, error) in
if (error != nil) {
print("error=\(String(describing: error))")
return
} // end if
self.user = User()
do {
let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? [String : AnyObject]
if let parseJSON = json?["data"] as? [[String : AnyObject]] {
for userFromJson in parseJSON {
let userData = User()
if let uid = userFromJson["uid"] as? String,
let username = userFromJson["username"] as? String,
let networth = userFromJson["networth"] as? String,
let avatar = userFromJson["avatar"] as? String {
userData.uid = Int(uid)
userData.username = username
userData.networth = networth
userData.avatar = avatar
self.usernameLabel.text = username
self.networthLabel.text = networth
self.avatarImageView.downloadImage(from: avatar)
circularImage(photoImageView: self.avatarImageView)
} // end if
self.user = userData
} // end for
} // end if
DispatchQueue.main.async {
print("Username: \(self.user.username)")
self.reloadView()
}
} catch let error {
print(error)
}
}
task.resume()
}

Answer 1

Firstly, call fetch user in viewWillAppear like this:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
fetchUser()
}
Then, change the code here like I did, don't use the reloadView function you had, instead, update the UI elements on the main thread at the end of the fetchUser function. I also changed it so you weren't updating the UI twice because you have 4 lines at the bottom of the if let uid = ... statement in fetchUser which updated UI elements that wasn't in the main thread which is why in my version I removed those 4 lines of code. Let me know if this worked for you.
let task = URLSession.shared.dataTask(with: urlRequest as URLRequest) { (data, response, error) in
if (error != nil) {
print("error=\(String(describing: error))")
return
} // end if
self.user = User()
do {
let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? [String : AnyObject]
if let parseJSON = json?["data"] as? [[String : AnyObject]] {
for userFromJson in parseJSON {
let userData = User()
if let uid = userFromJson["uid"] as? String,
let username = userFromJson["username"] as? String,
let networth = userFromJson["networth"] as? String,
let avatar = userFromJson["avatar"] as? String {
userData.uid = Int(uid)
userData.username = username
userData.networth = networth
userData.avatar = avatar
} // end if
self.user = userData
} // end for
} // end if
DispatchQueue.main.async {
self.usernameLabel.text = user.username
self.networthLabel.text = "$" + NumberFormatter.localizedString(from: Int((user.networth)!)! as NSNumber, number: NumberFormatter.Style.decimal)
self.avatarImageView.downloadImage(from: user.avatar!)
circularImage(photoImageView: self.avatarImageView)
}
} catch let error {
print(error)
}
}
task.resume()

Answer 2

Two suggestions:
strictly speaking, all accesses to UIView object should be on the main thread. You're dispatching to the main thread to call reloadView, but should probably also do it when you're settings the "username" and "net worth" values on the labels
are you sure that the labels are blank? Could it be an autolayout problem instead? (Try setting the background colour of the labels to yellow, to check that they're the correct size. Sometimes autolayout can squash views down to nothing if there are conflicting constraints)