Error trying to transfer data from variable between storyboards - ios

Question

I have a game where I store the value of the high score of a player as "highScore", in the first view controllers.
What I want to do is to try to transfer this variable data, to the second view controller.
I entered in the following code in the first view controller's storyboard.
Btw, highscore2, is the variable that I delcared in the second view controller, to store the data from the first highscore variable.:
override func prepareForSegue(segue: UIStoryboardSegue!, sender:AnyObject!)
{
if (segue.identifier == "segueTest")
{
var svc = segue!.destinationViewController as! viewTwo;
svc.highScore2 = "High Score \(highScore)"
}
}
Now here is the code in my second view controller (viewTwo):
class viewTwo: UIViewController
{
#IBOutlet var highScoretwolbl: UILabel!
var highScore2:String!
override func viewDidLoad() {
highScoretwolbl.text = highScore2
}
}
For some reason, the code compiles, but the high score is not displayed, and is "nil".

Answer 1

Avoid forced unwrapping.
if let svc = segue.destinationViewController as? viewTwo{
svc.highScore2 = "High Score \(highScore)"
}
Then put in a breakpoint and make sure you got to all of these lines.

Answer 2

As stated in other answers, viewDidLoad only gets fired once. Since you
are using a forced unwrapped string, it is initially nil. It (highScore2) won't get a value until you set it which happens after viewDidLoad. Add some print statements so you can see the sequence of events.
Your best option is to use viewWillAppear. This will get fired every time
your view appears. This is what you want.
You don't need to use a force unwrapped variable. Just make a string a
make it empty initially.
override func prepareForSegue(segue: UIStoryboardSegue, sender:AnyObject?)
{
if segue.identifier == "segueTest"
{
if let svc = segue.destinationViewController as? viewTwo {
print("setting score in prepareForSegue")
svc.highScore2 = "High Score \(highScore)"
}
else {
print("something bad happened")
}
}
}
class viewTwo: UIViewController
{
#IBOutlet var highScoretwolbl: UILabel!
// The following uses forced upwrapping which means it could be nil
// if you never set it and your app will crash.
// var highScore2: String!
// Instead, do this:
var highScore2: String = ""
override func viewWillAppear(animated: Bool) {
// putting this here will ensure that every time the screen
// is shown, the label will get set from the string.
highScoretwolbl.text = highScore2
}
}

Answer 3

If I recall correctly, the viewDidLoad method is called only once when the view controller is first initialized. So you are setting the highScoretwolbl variable before highScore2 actually has any data, this is why it is nil.
I would recommend setting the text inside viewWillAppear so it updates every time the segue happens.
So something like
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(true)
highScoretwolbl.text = highScore2
}
Here is a reference to the lifecycle of all the methods of a view controller. View controller lifecycle