func filterValues(search: String, scope: Scopes = .title) {
   if search.isEmpty {
      filteredItems = userData.sorted(by: { $0.title < $1.title })
   } else {
      let list = userData.filter( { item in
         let value = scope == .title ? item.title : item.author
         return value.localizedStandardContains(search)
      })
      filteredItems = list.sorted(by: { $0.title < $1.title })
   }
}