如何将AdMob GADBannerView添加到每个视图

import GoogleMobileAds

class ViewController: UIViewController, GADBannerViewDelegate {
    var bannerView: GADBannerView!

    override func viewDidLoad() {
        super.viewDidLoad()

        bannerView = GADBannerView(adSize: kGADAdSizeBanner)
        bannerView.adUnitID = "YOUR_AD_UNIT_ID"
        bannerView.rootViewController = self
        bannerView.delegate = self

        let request = GADRequest()
        request.testDevices = [kGADSimulatorID] // 仅用于测试，发布时请移除此行代码
        bannerView.load(request)

        // 将广告视图添加到每个视图中
        for subview in view.subviews {
            view.addSubview(bannerView)
            view.bringSubviewToFront(bannerView)
        }
    }
}