How to bring value from a UIviewController using delegate without instantiating object - swift

Question

I have 3 UIViewControllers say:
v1ViewController
v2ViewController
v3ViewController.
I have pushed controllers as v2 on v1 and v3 on v2.
Now I want to bring some value back to v1ViewController from v3ViewController using delegates.
On v3Viewcontroller I wrote it:
for vc in self.navigationController!.viewControllers{
if vc is v1ViewController{
delegate?.returnFilteredImage(imageView.image!)
self.navigationController?.popToViewController(vc, animated: true)
}
}
How can I use delegates because in v1ViewController I haven't create object of v3Viewcontroller; consequently I cannot connect delegate to self.
So how can i do that.

Answer 1

1. Using delgates
create a protocol and implement in your firstviewcontroller
protocol My {
func returnFilteredImage(image: UIImage)
}
class FirstViewController: UIViewcontroller, My {
...
func returnFilteredImage(image: UIImage) {
}
}
and in your thirdViewController create a property and assign FirstViewController delegate to this.
class ThirdViewController: UIViewController {
var delegate: My?
...
override func viewDidLoad() {
super.viewDidLoad()
for vc in self.navigationController!.viewControllers{
if vc is FirstViewController {
let vc1 = vc as! FirstViewController
self.delegate = vc1
self.delegate?.returnFilteredImage(imageView.image!)
self.navigationController?.popToViewController(vc, animated: true)
}
}
}
}
2. Using local notifications
check here
You can do this using local notifications
class FirstViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
//add observer
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.didgetImage(_:)), name: "receiveImageNotification", object: nil)
}
func didgetImage(notification: NSNotification) {
if let image = notification.userInfo?["image"] as? UIImage {
// do something with your image
}
}
}
and from third view controller, first notification
let imageDataDict:[String: UIImage] = ["image": image]
NSNotificationCenter.defaultCenter().postNotificationName("receiveImageNotification", object: self, userInfo: imageDataDict)
Hope this helps :)