Passing data from viewcontroler to tab viewed controllers in swift - ios

Question

I have this login form:
import UIKit
class LoginViewController: UIViewController {
var user : LoginUser?
#IBAction func btnLoginPressed(_ sender: Any) {
if self.textFieldLogin.text?.isEmpty ?? true || self.textFieldPassword.text?.isEmpty ?? true {
self.errorLoginMessage(txt: "Error", title: "Error")
} else {
let cms = ServerConnect()
cms.checkUsersLogin(login: self.textFieldLogin.text, password: self.textFieldPassword.text, completion: { (data) in
switch(data) {
case .succes(let data):
var actionToRun: ()-> Void
let decoder = JSONDecoder()
self.user = try? decoder.decode(LoginUser.self, from: data)
dump(self.user)
// we have an user
if ((self.user?.id ) != nil) {
actionToRun = {
self.performSegue(withIdentifier: "toLoginUser", sender: self)
}
}
// we have an error
else if let json = try? JSONSerialization.jsonObject(with: data, options: []),
let dictionary = json as? [String: Any],
let message = dictionary["komunikat"] as? String,
let title = dictionary["error"] as? String {
// we have an error
actionToRun = {
self.errorLoginMessage(txt: message, title: title)
}
}
// default error
else {
actionToRun = {
self.errorLoginMessage(txt: "Podany login lub hasło jest błędny!!", title: "Błąd")
}
}
DispatchQueue.main.async {
actionToRun()
}
case .error(let error):
print("Error 104: \(error)")
}
})
}
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?){
if segue.identifier == "toLoginUser" {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let tabVC = storyboard.instantiateViewController(withIdentifier: "MainVC") as! UITabBarController
self.present(tabVC, animated: true, completion: {
let vc = tabVC.selectedViewController as! NewsViewController
vc.loggedUser = self.user
})
}
}
func errorLoginMessage(txt: String, title: String){
let alertController = UIAlertController(title: title, message: txt, preferredStyle: .alert)
alertController.addAction(UIAlertAction(title: "Ok", style: .cancel, handler: { (action: UIAlertAction!) in
}))
self.present(alertController, animated: true, completion: nil)
}
}
The object is built correctly.
I would like to pass my object from the login view to tab viewed controllers.
I am receiving the object like this:
class NewsViewController: UIViewController {
var loggedUser : LoginUser?
override func viewDidLoad() {
super.viewDidLoad()
print("check object: \(loggedUser)")
dump(loggedUser)
}
#IBAction func testBtnPressed(_ sender: Any) {
print("check object: \(loggedUser)")
dump(loggedUser)
}
}
Unfortunately this code does not work and I always get nil.
My full source code: https://bitbucket.org/trifek/karta-nauka/src/master/
Can I ask for help?

Answer 1

It is not good idea to pass info view controller to view controller which is used by almost all of your view controller's
Like Login information which contains info that is nearly used by all of the screen
Good idea is to create Global Shared class which will store your all global information which is shared among the application.
public final class AppGlobalManager {
static let sharedManager = AppGlobalManager()
var loggedUser : LoginUser?
}
Now whenever user login you can
AppGlobalManager.sharedManager.loggedUser = object
And when user logout
AppGlobalManager.sharedManager.loggedUser = nil
Hope it is helpful

Answer 2

If you are already using segues in the storyboard, you don't have to get the desired view controller from the UIStoryboard, the segues itself provides the destination view controller.
Example:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "toLoginUser" {
let tabVC = segue.destination as! UITabBarController
// assuming that `NewsViewController` is the first view controller in the tabbar controller:
let destinationViewController = tabVC.viewControllers?[0] as! NewsViewController
destinationViewController.loggedUser = self.user
}
}
Since you are aiming to pass the LoginUser object to one of the tabbar view controllers, you could get it from the tabbar viewControllers array -as mentioned in the code snippet above-.