How to Updatie a uitextview from an external source. - ios

Question

I want to be able to update my uitextview by calling a method within my view. With this code I get a runtime error:
Unexpectedly found nil while unwrapping an Optional value
If I comment out the vw.updateTerm(...) line it runs. Ultimately, I want to update a uitextview with data updated from BLE and/or http request. Any help or direction would be most appreciated.
My playground swift 3 code looks like this:
import UIKit
import PlaygroundSupport
public class TextViewController : UIViewController {
public var textView : UITextView!
override public func loadView() {
textView = UITextView()
textView.text = "Hello World!\nHello Playground!"
self.view = textView
}
func updateTerm(textToUpdate: String) {
self.textView.text.append(textToUpdate)
}
}
let vw = TextViewController()
vw.updateTerm(textToUpdate: "here you go")
PlaygroundPage.current.liveView = vw

Answer 1

The problem is that loadView is still not called at the moment when you are trying to updateTerm, which means that textView is nil in the loadView for the vw instance.
As far as textView is declared as a forced-unwrapped property, any attempt to use it while it is nil (as in your case) will cause a runtime error.
You should make it either a regular optional:
public var textView : UITextView?
override public func loadView() {
textView = UITextView()
textView?.text = "Hello World!\nHello Playground!"
self.view = textView
}
func updateTerm(textToUpdate: String) {
self.textView?.text.append(textToUpdate)
}
or, for example, a lazy property (if suitable in your case):
lazy public var textView = UITextView()
override public func loadView() {
textView.text = "Hello World!\nHello Playground!"
self.view = textView
}
func updateTerm(textToUpdate: String) {
self.textView.text.append(textToUpdate)
}
More info can be found here.