iOS - Launch review if it's the first time opening and ad if it's not

review.swift

let when = DispatchTime.now() + 1 // change 1 to desired number of seconds
let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")
DispatchQueue.main.asyncAfter(deadline: when) {
        if #available(iOS 10.3, *){
                if !launchedBefore {
                        SKStoreReviewController.requestReview()
                        UserDefaults.standard.set(true, forKey: "launchedBefore")
                } else {
                        self.interstitialAd = self.createAndLoadInterstitial()
                }
        }       
}