我有 NestJS 应用程序,它与 YoutubeAPI 交互并从中加载视频。
有一个特殊方法很重要,它就是下面的 loadVideos
。方法本身内部有多个异步,一旦一切完成,我需要使用 videoIdMap
属性
private loadVideos(
playListId: string,
channel: Channel,
nextPageToken: string,
stopLoadingOnVideoId: string,
) {
const baseUrl = YoutubeService.VIDEO_URL_SNIPPET_BY_ID + playListId;
const response = this.httpService
.get(nextPageToken ? baseUrl + '&pageToken=' + nextPageToken : baseUrl)
.pipe(map((response) => response.data));
response.subscribe((data) => {
data.items.forEach((item) => {
if (stopLoadingOnVideoId && item.snippet.resourceId.videoId === stopLoadingOnVideoId) {
return;
}
this.prepareVideoEntity(item.snippet, channel).then((partialVideo) =>
this.videoService.create(partialVideo).then((video) => {
this.videoIdMap[video.youtubeId] = video.id;
}),
);
});
if (data.nextPageToken) {
this.loadVideos(
playListId,
channel,
data.nextPageToken,
stopLoadingOnVideoId,
);
}
});
}
对我来说理想的解决方案是以某种方式使 loadVideos
异步,这样我以后就可以这样做:
public methodWhichCallLoadVideos(): void {
await loadVideos(playListId, channel, null, stopLoadingOnVideoId)
// My code which have to be executed right after videos are loaded
}
我尝试过的每个解决方案最终都会导致 this.videoIdMap
成为空对象或出现编译问题,因此任何想法都非常受欢迎。
最佳答案
您可以切换到 Promise 而不是 Observables,从而将该方法转变为只要 data
具有 nextPageToken
就会重复出现的异步方法:
private async loadVideos(
playListId: string,
channel: Channel,
nextPageToken: string,
stopLoadingOnVideoId: string,
) {
const baseUrl = YoutubeService.VIDEO_URL_SNIPPET_BY_ID + playListId;
const response = await this.httpService
.get(nextPageToken ? url + '&pageToken=' + nextPageToken : url).toPromise();
const { data } = response;
for (const item of data.items) {
if (stopLoadingOnVideoId && item.snippet.resourceId.videoId === stopLoadingOnVideoId) {
continue;
}
const partialVideo = await this.prepareVideoEntity(item.snippet, channel);
const video = await this.videoService.create(partialVideo)
this.videoIdMap[video.youtubeId] = video.id;
}
if (data.nextPageToken) {
await this.loadVideos(
playListId,
channel,
data.nextPageToken,
stopLoadingOnVideoId,
);
}
}
在调用者中,您只需等待 loadVideos(...)
:
private async initVideoIdMap(...) {
await this.loadVideos(...);
// this.videoIdMap should be correctly populated at this point
}
关于express - 如何等待所有异步调用完成,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/64374671/