How to pass a data to a nested controller (UIContainerView)? - ios

Question

I've searched everywhere for a solution but nothing. I have two view controllers and I want to pass data from viewController.swift to resultViewController.swift (the container view), i've succeeded to send data when I run it. but when i clicked increase button I can't send data again.
ViewController.swift:
class ViewController: UIViewController {
var result: Int = 1
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
// performSegueWithIdentifier("sendResult", sender: <#AnyObject?#>)
}
#IBAction func increas(sender: AnyObject) {
result++
performSegueWithIdentifier("sendResult", sender: self)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "sendResult"{
var resultVC = segue.destinationViewController as! ResultViewController
resultVC.result = self.result
}
}
}
ResultViewController.swift:
class ResultViewController: UIViewController {
var result: Int!
#IBOutlet weak var resultLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
resultLabel.text = "\(result)"
}
}

Answer 1

Ok. Here's some working code.
First, remove your increase method and unhook it from your button in the Connections Inspector. Then delete your old segue in Interface Builder and create a new segue by dragging from the button to ResultsViewController. Make sure you give the segue a "sendResult" identifier in Interface Builder. In ViewController:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "sendResult" {
result++
var rvc = segue.destinationViewController as! ResultViewController
rvc.result = result
}
}
And then in ResultsViewController:
#IBOutlet weak var resultLabel: UILabel!
var result : Int = 0
override func viewDidLoad() {
super.viewDidLoad()
resultLabel.text = "\(result)"
// Do any additional setup after loading the view.
}

Answer 2

Nested ViewControllers are a bit tricky to use because from the parent controller point of view, all they see is a UIView (there is no rootViewController or nestedViewController property, which would be very nice to have).
The best way I have found to send/read data to/from the nested controller is by adding a reference to it on the parent controller.
It turns out that prepareForSegue is called after viewDidLoad for all nested view controllers. Then it is never called again, unless you call it manually. But you shouldn't and will not need to do that.
Here is how you can get a reference to the nested controller to use later in your code:
class ViewController: UIViewController {
var result: Int = 1
private var resultVC: ResultViewController? // Keep it optional
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
#IBAction func increas(sender: AnyObject) {
result++
// Update result value, keep optional reference for security
// Here you could write & read values, call methods, etc.
resultVC?.result = result
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "sendResult" {
// Save reference to child view controller (use optional)
resultVC = segue.destinationViewController as? ResultViewController
}
}
}
Once you have the reference to the nested view controller, you can use it anywhere in the code. To be safe, always use it with ?.