异步不等待回调中的等待完成

Question

Im still a rookie with async and awaits, but this is what Im working with.

    async function _getImageURLs(folder) {
         if (!id) return;

         foo.AWSS3Helper.GetImageUrls(so, function (imageUrls) {
             return await imageUrls;
         });
    }

The fuction _getImageURLs() is still returning without waiting for the AWSS3Helper.GetImageUrls finishes. Im guessing it has something to do with being inside a callback function. Does the callback need to be async as well?

Answer 1

Use await on the function not on the return statement

  async function _getImageURLs(folder) { if (!id) return; foo.AWSS3Helper.GetImageUrls(so, await function (imageUrls) { return imageUrls; }); } 

Answer 2

Try it with observables. Something like this...

   function _getImageURLs(folder) {
             if (!id) return;

             const imageUrlObservable = of(foo.AWSS3Helper
                  .GetImageUrls(so, function (imageUrls) {
                     return imageUrls;
                   })
             );

             imageUrlObservable.subscribe({
                 next(imageUrL) { console.log(imageUrL) },
                 complete() { console.log('Finished sequence'); }
             });


        }

Answer 3

As far as i see there are no promises here, you have a callback based mechanism on the api so using async/await seems pointless

you should pass a callback to the method and invoking it as soon as you have the result available

function _getImageURLs(folder, callback) {
     if (!id) callback();

     foo.AWSS3Helper.GetImageUrls(so, function (imageUrls) {
         callback(imageUrls);
     });
}

_getImageURLs("somefolder", function(result) {
   console.log(result);
   // do whatever you want here with the result
 };