Pass one variable from one viewcontroller to another viewcontroller - ios

Question

I new to swift language and know this question is duplicated.I`ve found several similar question and answer, but i could not able to figure out the problem.
I want to pass the value of detectionString variable to ResultViewController from ScanViewController.
ScanViewcontroller as below:
import UIkit
class ScanViewController: UIViewController {
var detectionString : String!
override func viewDidLoad() {
super.viewDidLoad()
detectionString = “SomeDetectedString”
}
override func prepareForSegue(segue: UIStoryboardSegue,sender: AnyObject!) {
if (segue.identifier == "MySegue") {
var svc = segue.destinationViewController as ResultViewController;
svc.detectedString = detectionString
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
The ResultViewController as below:
import UIkit
class ResultViewController: UIViewController {
var detectedString: String!
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor=UIColor.whiteColor()
println(detectedString)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
The println(detectedString) gives me no result. question is that how can get the variable from ScanViewController?

Answer 1

This may sound bizarre but there is nothing wrong with your code BUT it does not work as is. I used your code identically and it ignored the segue. Then I embedded ScanViewController in a navigation controller in the storyboard. I also put a call to self.performSegueWithIdentifier("MySegue", sender: self) in the ScanViewController viewDidLoad to initiate the segue. Then everything works like a charm. Your prepareForSegue is fine. Yuvrajsinh's suggestion is fine but not necessary (I tried it after changing DetailVC to ResultViewController). Without the navigation controller nothing works. segue.identifier is a string and it will work in a straight Swift string comparison.
Here is the code for ScanViewController:
import UIkit
class ScanViewController: UIViewController {
var detectionString : String!
override func viewDidLoad() {
super.viewDidLoad()
detectionString = "SomeDetectedString"
println(detectionString)
self.performSegueWithIdentifier("MySegue", sender: self)
}
override func prepareForSegue(segue: UIStoryboardSegue,sender: AnyObject!) {
if (segue.identifier == "MySegue" || segue.identifier == "SegueFromButton") {
println("prepareForSegue")
var svc = segue.destinationViewController as ResultViewController;
svc.detectedString = detectionString
println("svc.detectedString: \(svc.detectedString)")
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
and for ResultViewController:
import UIkit
class ResultViewController: UIViewController {
var detectedString: String!
override func viewDidLoad() {
println("Result Load View")
super.viewDidLoad()
self.view.backgroundColor=UIColor.whiteColor()
println("detectedString in Result: \(detectedString)")
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}

Answer 2

your segue.identifier == "MySegue" is some how not comparing in the way it should.
replace your code with following function and you are done.
override func prepareForSegue(segue: UIStoryboardSegue,sender: AnyObject!) {
let segueName: String = segue.identifier!;
if (segueName == "MySegue") {
var svc = segue.destinationViewController as DetailVC;
svc.detectedString = detectionString
}
}

Answer 3

There are three options for you:
use prepareForSeguemethod to get the target ViewController and set up the property
set up delegate relationship between the two ViewControllers to communicate
set up Observer with NSNotificationCenter