getCoverArtUrl function Null safety

Future<String?> getCoverArtUrl(
  1. String mangaID,
  2. int? res
)

Implementation

Future<String?> getCoverArtUrl(String mangaID, int? res) async {
  var reso = res ?? '';
  var data = await getCoverArt(mangaID);
  if (data != null) {
    var filename = data.results[0].data.attributes.fileName;
    if (reso == 256 || reso == 512) {
      return 'https://uploads.mangadex.org/covers/$mangaID/$filename.$reso.jpg';
    } else {
      return 'https://uploads.mangadex.org/covers/$mangaID/$filename';
    }
  } else {
    print(
        'No cover art for manga ID $mangaID found, make sure the manga ID is correct and manga ID is not an empty String.');
  }
}