问题
I'm currently learning swift and I'm trying to learn of instanciation from storyboard works, but the error I'm facing now isn't documented very much.
I created a viewcontroller in my main storyboard and I specified it's type as a custom class I called previously SimpleNewsViewController, here's the code of my class, it is'nt complicated:
class SimpleNewsViewController: UIViewController {
@IBOutlet weak var myImage: UIImageView!
@IBOutlet weak var myLabel: UILabel!
@IBOutlet weak var myText: UITextView!
var event: Events!
override func viewDidLoad() {
super.viewDidLoad()
}
}
On my main storyboard here is the custom ViewController I specified : My Storyboard implementation
Now here's the problem : In my code I instanciate my ViewController thanks to the instanciateViewController(identifier: "NewsView") and then I try to set my 3 attributes like in this piece of code :
...
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let controller = storyboard.instantiateViewController(withIdentifier: "NewsView") as! SimpleNewsViewController
//controller.myImage.image = UIImage(named: "image.jpg")
//controller.myText.text = "this is an example that can be really long"
//controller.myTitle.text = "this is a title example
self.navigationController?.pushViewController(controller, animated: true)
...
If I un-comment the three lines I have an error saying:
Fatal error: Unexpectedly found nil while unwrapping an Optional value
The IDE also displays the error code and the thread (if that can help): The error
回答1:
Right after instantiating the controller the outlets are not connected yet, you have to declare temporary variables and set the outlet properties in viewDidLoad()
...
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let controller = storyboard.instantiateViewController(withIdentifier: "NewsView") as! SimpleNewsViewController
controller.tempImage = UIImage(named: "image.jpg")
controller.tempLabel = "this is an example that can be really long"
controller.tempText = "this is a title example
self.navigationController?.pushViewController(controller, animated: true)
...
class SimpleNewsViewController: UIViewController {
@IBOutlet weak var myImage: UIImageView!
@IBOutlet weak var myLabel: UILabel!
@IBOutlet weak var myText: UITextView!
var tempImage : UIImage?
var tempLabel = ""
var tempText = ""
var event: Events!
override func viewDidLoad() {
super.viewDidLoad()
myImage.image = tempImage
myLabel.text = tempLabel
tempText.text = tempText
}
来源：https://stackoverflow.com/questions/44445895/get-attribute-of-viewcontroller-created-with-storyboard