Returning an image from Firebase storage within Reactjs-CodePudding

I have a function which goes off to retrieve an image from Firebase Storage:

import {
  getStorage,
  ref,
  getDownloadURL
} from 'firebase/storage';

const storage = getStorage();

export async function getImage(location) {
  const ImageURL = await getDownloadURL(ref(storage, location));
  return await ImageURL;
}

This is then called within a React component:

import { getImage } from 'API/Storage/getImage';

const EventPage = (props) => {
  return (
    <div>
      <img src={getImage('image.jpg')}
    </div>
  );
}

export default EventPage;

However the image doesn't display and instead shows: <img src="[object Promise]" alt="Show Image">

What's the best way of resolving the promise? Console logging ImageURL within the getImage function returns the URL as expected.

CodePudding user response：

You need to wait for the promise to resolve. You can fetch the data in a useEffect and store the value in a useState.

Here's a basic example:

import { getImage } from 'API/Storage/getImage';

const EventPage = (props) => {
  const [image, setImage] = useState();

  useEffect(async () => {
    const image = await getImage('image.jpg');
    setImage(image);
  }, []);

  return (
    <div>
      {image ? <img src={image} /> : "Loading image"}
    </div>
  );
}

export default EventPage;

The useEffect in the above example doesn't account for the case when your component is unmounted while still fetching the data. An implementation that accounts for that looks like so:

useEffect(() => {
  let wasUnmounted = false;
  getImage('image.jpg').then((image) => {
    if (wasUnmounted) return;
    setImage(image);
  });
  return () => {
    wasUnmounted = true;
  };
}, []);

Notice that the callback provided to useEffect isn't async. That's because async functions return a promise. To be able to detect that the component was unmounted we need to return a callback (it will be called when the component is unmounted, because of the empty array passed as a second argument). Please read more about useEffect here: https://reactjs.org/docs/hooks-reference.html#useeffect