Question

我尝试设置以下方法，一旦执行了所有show.getVideosForShow（）成功块并附加了所有视频，就执行成功块。注意：show.getVideosForShow（）是异步的，可能需要几秒钟才能得到结果。有人可以提供一些帮助吗？

private func getNextVideoRecommendations(success: ([Video]) -> ()) {
    var relatedVideos = [Video]()
    if let relatedShows = self.videoCurrentlyPlaying?.show?.getShowsWithSameGenre(fetchLimit: 3) {
        for show in relatedShows {
            show.getVideosForShow(tvSeason: nil, longForm: true, sortType: VideoSort.Latest, success: { (videos: [Video]) in
                print("Found Related Show: \(show.title)")
                if videos.count > 0 {
                    relatedVideos.append(videos[0])
                }
            })
        }
        print("Finished all operations")
        success(relatedVideos)
    }
}

Answer 1

这是dispatch groups的一个很好的用例，它允许您在所有操作完成后提交另一个块：

private func getNextVideoRecommendations(success: ([Video]) -> ()) {
    var relatedVideos = [Video]()
    if let relatedShows = self.videoCurrentlyPlaying?.show?.getShowsWithSameGenre(fetchLimit: 3) {
        let group = dispatch_group_create()
        for show in relatedShows {
            dispatch_group_enter(group)  // start tracking one unit of work
            show.getVideosForShow(tvSeason: nil, longForm: true, sortType: VideoSort.Latest, success: { (videos: [Video]) in
                print("Found Related Show: \(show.title)")
                if videos.count > 0 {
                    relatedVideos.append(videos[0])
                }
                dispatch_group_leave(group)  // finish one unit of work
            })
        }
        dispatch_group_notify(group, dispatch_get_main_queue()) {  // and when done...
            print("Finished all operations")
            success(relatedVideos)
        }
    }
}

使用数组进行回调

1 个答案: