Admob奖励视频GADRewardBasedVideoAd在目标c IOS中

我正在尝试奖励使用AdMob观看视频的用户。例如，每X次搜索，应向用户显示向其显示结果的视频。我对视频广告一无所知。您能帮我吗？请参阅下面的代码：

[GADRewardBasedVideoAd sharedInstance].delegate = self;
GADRequest *request1 = [GADRequest request];

  request1.testDevices = kGADSimulatorID;
[[GADRewardBasedVideoAd sharedInstance] loadRequest:[GADRequest request]
                                       withAdUnitID:@"ca-app-pub-4719922286387557/6283056409"];
if ([[GADRewardBasedVideoAd sharedInstance] isReady]) {
    [[GADRewardBasedVideoAd sharedInstance] presentFromRootViewController:self];
}