Why cannot use if statement in AppDelegate?

Question

why I cannot pass the constant in if statement?

 if UIDevice.current.orientation.isLandscape{
        let storyboard = UIStoryboard(name: "landscape", bundle: nil)
        let initialViewController = storyboard.instantiateViewController(withIdentifier: "landscape")
    }else{
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let initialViewController = storyboard.instantiateViewController(withIdentifier: "ViewController")
    }
    

    self.window?.rootViewController = initialViewController

Answer 1

You need to insert the error line inside the if else block as of scope

if { 
  let initialViewController = //// 
  self.window?.rootViewController = initialViewController
}
else { 
  let initialViewController = //// 
  self.window?.rootViewController = initialViewController
}

OR

var initialViewController:UIViewController!
if { 
  initialViewController = ////
}
else { 
  initialViewController = ////
}
// use it here