如何创建 RxJS Observable 使其在回调函数完成时返回一个值 [英] How to create an RxJS Observable such that it returns a value when call back function completes

问题描述

我需要创建一个 RxJS Observable，以便它在回调函数完成时返回一个值.

I need to create an RxJS Observable such that it returns a value when call back function completes.

下面是代码，我试过了.

Below is the code, I have tried.

我想在订阅 loadMarkerImages 函数的调用者中返回要返回的资源"

I want to return 'resources' to be returned in the caller subscribing to loadMarkerImages function

loadMarkerImages(markerNameAndImageUrlMap) {
    let loader = new PIXI.loaders.Loader();
    for (let markerKey in markerNameAndImageUrlMap) {
      let imageUrl = markerNameAndImageUrlMap[markerKey];
      loader.add(markerKey, imageUrl);
    }
    Observable.create()
    return defer(() => {
      loader.load((loader, resources) => {
        return of(resources);
      });
    })
}

推荐答案

请参阅文档 关于如何创建一个 observable:

See the documentation for how to create an observable:

return new Observable(subscriber => {
  let loader = new PIXI.loaders.Loader();
  for (let markerKey in markerNameAndImageUrlMap) {
    let imageUrl = markerNameAndImageUrlMap[markerKey];
    loader.add(markerKey, imageUrl);
  }
  loader.load((loader, resources) => {
    subscriber.next(resources);
    subscriber.complete();
  }); 
}

不过，如果 loader.load() 调用可能失败，请确保也处理错误情况.否则返回的 observable 永远不会发出，永远不会完成，永远不会出错.

Make sure to also handle the error case if the loader.load() call can fail, though. Otherwise the returned observable will never emit, never complete, and never error.

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