hasChanged method
Check if any member of a FileCollection has been modified since the last time someone checked with this method.
The key
argument is used to consider whether changes have happened
since last time the check was made with the exact same key.
Returns false if the FileCollection is empty.
Implementation
Future<bool> hasChanged(FileCollection fileCollection,
{String key = ''}) async {
return !await findChanges(fileCollection, key: key).isEmpty;
}