Can't go from a view to another after doing some instructions - ios

Question

I have this implementation in a part of my app:
Why when I click on "cerca per ISBN" button it goes to the tableView without doing the instructions that I have written?
This is the code of the "cerca per ISBN" button that I click:
#IBAction func ISBNButtonClick(_ sender: Any) {
let libro = Libro.text! as String
if Libro.text!.isEmpty {
//Alert per segnalare i campi mancanti, oltre a caselle rosse
var myAlert = UIAlertController(title:"Attenzione\n", message:"Inserire il codice ISBN", preferredStyle:UIAlertControllerStyle.alert);
let okAction = UIAlertAction(title:"Ok", style:UIAlertActionStyle.default){ action in }
myAlert.addAction(okAction);
self.present(myAlert, animated:true, completion:nil);
// placeholder rosso se la text è vuota
Libro.attributedPlaceholder = NSAttributedString(string:"Digita qui...", attributes: [NSForegroundColorAttributeName: UIColor.red])
//se tutti i campi obbligatori sono stati inseriti, proseguo ad altri controlli
}else{
if(isNumeric(string: libro)){
if((libro.characters.count) < 13 || (libro.characters.count) > 13){
//Alert per segnalare l'ISBN più corto di 13 numeri
var myAlert = UIAlertController(title:"Attenzione\n", message:"L'ISBN deve essere di 13 cifre", preferredStyle:UIAlertControllerStyle.alert);
let okAction = UIAlertAction(title:"Ok", style:UIAlertActionStyle.default){ action in }
myAlert.addAction(okAction);
self.present(myAlert, animated:true, completion:nil);
}else{
//inviare dati al server
let myUrl = NSURL(string:"http://chuadiv.ddns.net/easytoschool/fetch_book_detailed.php");
let request = NSMutableURLRequest(url:myUrl as! URL);
request.httpMethod = "POST";
let postString = "name=\(libro)&mail=\(UserDefaults.standard.object(forKey: "userEmail") as? String)";
request.httpBody = postString.data(using: String.Encoding.utf8);
let task = URLSession.shared.dataTask(with: request as URLRequest){
data, response, error in
if error != nil{
print("error=\(error)")
return
}
var err: NSError?
do{
var json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSArray
if let parseJSON: NSArray = json{
for index in 0...parseJSON.count-1 {
print("ciao")
let libro = parseJSON[index] as! [String:Any]
print("\n\n",index,":\n")
let book = resultCell.init(bookId: libro["id"] as! String,bookName: libro["name"] as! String,bookAuthor: libro["author"] as! String,bookSchool: libro["school"] as! String,bookPrice: libro["price"] as! String,bookStatus: libro["status"] as! String,bookISBN: libro["isbn"] as! String,bookType: libro["type"] as! String,bookIdSeller: libro["idSeller"] as! String,bookNameSeller: libro["nameSeller"] as! String,bookSurnameSeller: libro["surnameSeller"] as! String)
book.printBook();
HomeViewController.booksArray.append(book)
}
}
}catch{
print("error=\(error)")
return
}
}
task.resume();
performSegue(withIdentifier: "homeToListBook", sender: self)
}
}else{
var myAlert = UIAlertController(title:"Attenzione\n", message:"Inserire solo numeri per la ricerca attraverso codice ISBN", preferredStyle:UIAlertControllerStyle.alert);
let okAction = UIAlertAction(title:"Ok", style:UIAlertActionStyle.default){ action in }
myAlert.addAction(okAction);
self.present(myAlert, animated:true, completion:nil);
}
}
}
I want that when I press the button it sets my array and after it goes to the tableView, but I can't

Answer 1

The issue is that completion block of dataTask will call async so it will call later and you are currently performing segue outside the completion block of it. So what you need to do is call performSegue inside the completion block of dataTask also on Main thread. Also use URL and URLRequest instead of NSURL and NS(Mutable)URLRequest
let myUrl = URL(string:"http://chuadiv.ddns.net/easytoschool/fetch_book_detailed.php")
let request = URLRequest(url:myUrl!)
request.httpMethod = "POST";
let postString = "name=\(libro)&mail=\(UserDefaults.standard.string(forKey: "userEmail")!)"
request.httpBody = postString.data(using: .utf8)
let task = URLSession.shared.dataTask(with: request as URLRequest){
data, response, error in
if error != nil{
print("error=\(error)")
return
}
var err: NSError?
do{
var json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? [[String:Any]]
if let parseJSON = json {
for libro in in parseJSON {
let book = resultCell.init(bookId: libro["id"] as! String,bookName: libro["name"] as! String,bookAuthor: libro["author"] as! String,bookSchool: libro["school"] as! String,bookPrice: libro["price"] as! String,bookStatus: libro["status"] as! String,bookISBN: libro["isbn"] as! String,bookType: libro["type"] as! String,bookIdSeller: libro["idSeller"] as! String,bookNameSeller: libro["nameSeller"] as! String,bookSurnameSeller: libro["surnameSeller"] as! String)
book.printBook();
HomeViewController.booksArray.append(book)
}
//Perform segue now
DispatchQueue.main.async {
performSegue(withIdentifier: "homeToListBook", sender: self)
}
}
}catch{
print("error=\(error)")
return
}
}
task.resume()
Note: In Swift use Swift native type array and dictionary instead of NSArray and NSDictionary.

Answer 2

you are appending items to an array of another instance, or even to some static var instead of passing it
what you should do is create class of Book with all properties
class Book {
let id: String
init(data: [String:Any]) {
self.id = data["id"] as? String ?? "" //or some other error handling
}
}
then create an array of books inside current UIViewController
var books: [Book] = []
then do something like
let book = Book(data: libro)
books.append(book)
to pass data you should create an array of books inside destination controller (HomeViewController)
set its DataSource and Delegate functions to create UITableViewCells using this array
and pass data like
override func prepare(for segue: UIStoryboardSegue, sender _: Any?) {
if segue.identifier == "homeToListBook" {
if let destinationVC = segue.destination as? HomeViewController {
destinationVC.books = self.books
}
}
}
EDIT:
and as Nirav D mentioned, segue should be called in main thread after data has been parsed, did not notice this