由异步创建未定义无法解决？

Question

I currently have the following scenario. I cant' really figure out why this is happening it might be to do with it not resolving in time or something else.

According to documentation on Expo. The following method would return an object.

MediaLibrary.getAlbumAsync('pleaseDontDownVote');

MediaLibrary is provides a users camera roll and the method getAlbumAsync is getting the album named 'pleaseDontDownVote'. I've confirmed MediaLibrary works, as it was used to create the album and also I've confirmed the album 'pleaseDontDownVote' appears on the device.

I then have another method which is:

savePictures = () => {
      let getCameraRoll = this.orderPhotoAlbum();
      getCameraRoll.then(cameraRollItem => console.log(cameraRollItem))
}

Here this is what I 'think' I'm doing, my method savePictures is executing this.orderPhotoAlbum in getCameraRoll then I'm waiting for it to execute so that I can proceed.

async orderPhotoAlbum() {
  await MediaLibrary.getAlbumAsync('pleaseDontDownVote');
}

The MediaLibrary method is wrapped in an async method so it would wait for the response. I'm thinking orderPhotoAlbum() would wait to get the response and then that would be passed to my "then". The console.log in getCameraRoll.then(cameraRollItem => console.log(cameraRollItem)) says undefined. Is this a problem with the way I'm managing the async/await?

NOTE: I tagged this js because I don't think it has to do with Expo all that much as it does with the async/await. I could be wrong thou.

Answer 1

orderPhotoAlbum isn't returning anything, hence the undefined .

async orderPhotoAlbum() {
  return await MediaLibrary.getAlbumAsync('pleaseDontDownVote');
}

Edit: As Jake mentioned, at this point the await and async are redundant. I kept them because it makes it really clear that the function returns a promise. It's just a matter of personal preference though.

Answer 2

orderPhotoAlbum() as it is currently written does not return the result of MediaLibrary.getAlbumAsync('pleaseDontDownVote'); , since await does not return by default like it seems you are expecting it to. Try changing it to:

function orderPhotoAlbum() {
  return MediaLibrary.getAlbumAsync('pleaseDontDownVote');
}

Note that is no longer an async function, but it still returns a Promise so .then will work on it.