ios – uiview get motion from swiftUI, ERROR unexpectedly discovered nil whereas implicitly unwrapping an Optionally available worth

I’ve Scrollview_Itemselect was written by swiftUI. I attempt to cross an motion from this struct to my UIViewController CLASS_A’s WBMode_change func. It really works OK however I bought an uncommon drawback when I attempt to convert Int to String.

struct Scrollview_Itemselect: View { //struct

    @State var emojisArray = ["A", "B", "C", "D"]
    @State var selectedIndex = 0

    let someView = CLASS_A()

    var physique: some View {
        VStack {
            ScrollView(.horizontal) {
                HStack {
                    ForEach(0..<emojisArray.depend) { merchandise in
                        emojiView(emoji: self.emojisArray[item],
                                  isSelected: merchandise == self.selectedIndex ? true : false)
                            .onTapGesture {
                               // print (merchandise)
                                self.selectedIndex = merchandise
                              // Name func in CLASS_A()
                                self.someView.WBMode_change(mode: self.selectedIndex)
                            }
                           // .body(width: 100, top: 120)
                    }
                }
            }
        }
    }
}

//right here is my class, I describe WBMode_change right here.
//WBMode_change shall be referred to as above, inside Scrollview_Itemselect struct. 
//[self.someView.WBMode_change(mode: self.selectedIndex)]
Class CLASS_A: UIViewController, UIScrollViewDelegate { //my class

    func WBMode_change(mode:Int){
        print("consequence", mode:Int) // print OK
        
        lbl_WBMode.textual content = String(mode) //ERROR right here
    }
}

I bought the print consequence positive however bought “unexpectedly discovered nil” when changing mode to String.

Then I modified some issues and tried this code under.

Class CLASS_A: UIViewController, UIScrollViewDelegate {
//nonetheless error even I do not use "mode" variable
    func WBMode_change(mode:Int){ //get motion from struct swiftUI
        let mode_number:Int = 10
        print("mode_number", mode_number)
        
        lbl_WBMode.textual content = String(mode_number)
    }

//no error
    func test_mode(){ //do not get motion from struct swiftUI
        let mode_number:Int = 10
        print("mode_number", mode_number)
        
        lbl_WBMode.textual content = String(mode_number)
    }
}

It nonetheless error after I simply put a textual content on it like this
lbl_WBMode.textual content = “Whats up”.

Is there anybody who is aware of what sort of this drawback is?