How do I delete a Firebase Storage file from URL

Question

how can I get a button to delete a file from Firebase Storage using a URL as a reference. The URL is retrieved from a Firestore collection field called "fileUrl" using the Firebase Storage getDownloadUrl method. When I try to delete, I receive an error and my app crashes.

Code:

onPressed: () async {
             if (newsDataModel.get('fileUrl') != null) {
             await FirebaseStorage.instance.refFromURL(newsDataModel.get('fileUrl')).delete();
             } else {
               return;
             }
             await newsDataModel.reference.delete().then((value) => Navigator.pop(context));
}

Error:

_AssertionError ('package:firebase_storage/src/firebase_storage.dart': 
 Failed assertion: line 112 pos 12: 'url.startsWith('gs://') || url.startsWith('http')': 
 'a url must start with 'gs://' or 'https://')

Answer 1

Realized that I had made a mistake. Some of the collections have fileUrl fields that are empty/null, so I was deleting collections that had null values and therefore returned an error.

New updated code:

onPressed: () async {
          try {
           if (hwDataModel.get('fileUrl') != null) {
            await FirebaseStorage.instance.refFromURL(hwDataModel.get('fileUrl')).delete()
            .then((value) => {
             hwDataModel.reference.delete().then((value) =>
              Navigator.pop(context))});
            } else if (hwDataModel.get('fileUrl') == null) {
               await hwDataModel.reference.delete().then(
                (value) => Navigator.pop(context));
             };
            } on FirebaseException catch (error) {
              Fluttertoast.showToast(
               msg: error.message.toString(),
               gravity: ToastGravity.TOP,
               backgroundColor: Colors.red,
               textColor: Colors.white);
             }
      },