I've found an acceptable answer for Objective-C here:
Play interstitial ad every 3rd game
But, I'm trying to do the same thing in Swift. I'm looking how to write the Static variable.
Here's the Objective-C code:
static int count = 0;
-(void) GameOver {
if(count != 0 && count % 3 == 0)
[HZInterstitialAd show];
count++;
}
private var count = 0
func GameOver {
if (count != 0 && count % 3 == 0) {
HZInterstitialAd.show()
}
count++
}