CODEWITHSUNDEEP
swiftmacosswiftui
QCD_IS_GOOD
QCD_IS_GOOD

Reputation: 465

Setting @Binding variable doesn't change the variable for some reason

My code is as follows:

class EditorWindow: NSWindow {
    @Binding var keycode : Int

    override func keyDown(with event : NSEvent) {
        super.keyDown(with: event)
        
        print("before", self.keycode, Int(event.keyCode))
        self.keycode = Int(event.keyCode)
        print("after",  self.keycode, Int(event.keyCode))
    }

    init(keycode : Binding<Int>){
        self._keycode = keycode
        super.init(contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),
                   styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
                   backing: .buffered, defer: false)   
    }
}

for detecting key-presses in a macOS app. It detects the key-presses, but for some reason it doesn't set the keycode @Binding variable , i.e. the value doesn't change in the 'before' and 'after' print statements. How can this be possible?

Edit:

For clarification, the keycode variable I am passing in during init is a @State variable:

struct ContentView: View {
    
    @State var keycode : Int = 0
    ...
}

...

class AppDelegate: NSObject, NSApplicationDelegate {

    var window: NSWindow!
    ...

    func applicationDidFinishLaunching(_ aNotification: Notification) {
        
        let contentView = ContentView(userData: UserData(text:""))
        window = EditorWindow(keycode: contentView.$keycode)
        ....
    }
}

Upvotes: 5

Views: 791

Answers (1)

Asperi
Asperi

Reputation: 257493

The @Binding variable must be bound to something (eg. @State), like

struct TestNSWindowBinding: View {
    @State var keyCode: Int = 0
    var body: some View {
        Text("Current key: \(keyCode)")
            .onAppear {
                let window = EditorWindow(keycode: self.$keyCode)
                window.makeKeyAndOrderFront(nil)
            }
    }
}

If it is not bound it just provide own initial state, consider it as external storage, so if no bound then no place to store value, so only default can be returned.

Upvotes: 4

Related Questions