Swift: Ensure urlSession.dataTask is completed in my function before passing result - swift

Question

Hello I have this function:
func planAdded(id:Int, user_id:Int) -> Int {
let locationURL = "myurl"
var planResult: Int = 0
let request = URLRequest(url: URL(string: locationURL)!)
let urlSession = URLSession.shared
let task = urlSession.dataTask(with: request, completionHandler:{
(data, response, error) -> Void in
DispatchQueue.main.async {
if let error = error {
print (error)
return
}
if let data = data {
let responseString = NSString(data: data, encoding: String.Encoding.utf8.rawValue)
planResult = responseString!.integerValue
}
}
})
task.resume()
print(planResult)
return planResult
}
What I am trying to do is to ensure that I got the result for planResult in tableView cellforrow at indexpath function.
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
...
case 4:
if (result == 1){
...
} else if (result == 2){
...
} else {
...
}
default:
cell.fieldLabel.text = ""
}
return cell
}
Here is my viewDidLoad function
override func viewDidLoad() {
super.viewDidLoad()
self.result = self.planAdded(1, 2)
}
For some reasons, this keeps returning 0; however, the print line is actually printing correct value. I did some research and I believe this is because of asychonous call of the dataTask. Is there a way I ensure that my function is actually completed and return the value for the indexpath function?
Thanks

Answer 1

The reason is, you are doing it in a wrong way! Because, once you intialize the class the UIViewController lifecycle starts. Once the viewDidLoad() is called it the UITableView is also updated with no data.
Also, you are calling API to get the data, you need to notify UITableViewDataSource to update data and here is how you can do that!
func planAdded(id:Int, user_id:Int) {
let locationURL = "myurl"
var planResult: Int = 0
let request = URLRequest(url: URL(string: locationURL)!)
let urlSession = URLSession.shared
let task = urlSession.dataTask(with: request, completionHandler:{
(data, response, error) -> Void in
DispatchQueue.main.async {
if let error = error {
print (error)
return
}
if let data = data {
let responseString = NSString(data: data, encoding: String.Encoding.utf8.rawValue)
self.result = responseString!.integerValue
self.tableView.reloadData()
}
}
})
task.resume()
}
And you are getting zero value because it's an async method. So get the data you need to use completionCallback.
func planAdded(id:Int, user_id:Int, completion: (result: Int) -> ()) {
let locationURL = "myurl"
var planResult: Int = 0
let request = URLRequest(url: URL(string: locationURL)!)
let urlSession = URLSession.shared
let task = urlSession.dataTask(with: request, completionHandler:{
(data, response, error) -> Void in
DispatchQueue.main.async {
if let error = error {
print (error)
return
}
if let data = data {
let responseString = NSString(data: data, encoding: String.Encoding.utf8.rawValue)
planResult = responseString!.integerValue
completion(planResult)
}
}
})
task.resume()
}
Usage:
override func viewDidLoad() {
super.viewDidLoad()
planAdded(1, 2){(value) in
self.result = value
self.tableView.reloadData()
}
}