下一集

let next = VideoAds(content: nextEpisode)
Task { nextLinear = try? await next.format(.linear); try? await nextLinear?.load() }

// 观众继续看下一集时：
ads.destroy()
ads = next
ads.track(player)     // 播放器现在播放下一集

func episodeFinished() {
    do {
        guard let postRoll else { return nextEpisode() }
        try postRoll.show()                  // 此时调用 destroy() 会结束它
    } catch {
        nextEpisode()                        // 没有展示
    }
}

func videoAd(_ ad: VideoAd, didEnd reason: VideoAd.EndReason) {
    if ad === postRoll { nextEpisode() }
}

func nextEpisode() {
    ads.destroy()                            // 在片尾广告的 didEnd 之后，绝不在之前
    ads = next
    ads.track(player)
}