Dart > Sort List<Map> by multiple keys

main.dart

extension SortBy on List {
  sortBy(List<String> keys) {
    this.sort((a, b) {
      for(int k=0; k<keys.length; k++) {
        String key = keys[k];
        int comparison = Comparable.compare((a[key]??""), (b[key]??""));
        if(comparison != 0){
          return comparison;
        }
      }
      return 0;
    });
  }
}

void main() {
  List<Map> items = [
    {'building': 'Main Building', 'room': 'Lounge'},
    {'building': 'Another Building', 'room': 'Study'},
    {'building': 'Main Building', 'room': 'Kitchen'},
    {'building': 'Main Building'},
    {'building': 'Another Building', 'room': 'Kitchen'},
  ];
  print(items);
  print('----');
  items.sortBy(['building', 'room']);
  print(items);
}