custom sort a string list in flutter

April 5, 2022

I have a list (in flutter):

loadedSummaryList = [
         'BILD',
         'DRIT',
         'VIMN',
         'WELT',
         'FLUTTER',
         'ALL'
       ];

, and I want to sort this list like:

['WELT', 'BILD', 'VIMN', 'DRIT', 'ALL', 'FLUTTER']

in other words, I want to sort the first four elements of the list always like ‘WELT’, ‘BILD’, ‘VIMN’, ‘DRIT’, and then alphabetically.
I tried it like this:

  List<String> sortList = ['WELT', 'BILD', 'VIMN', 'DRIT'];
       
  loadedSummaryList.sort(
          (a, b) {
            int aIntex = sortList.indexOf(a.name);
            int bIntex = sortList.indexOf(b.name);
            return aIntex.compareTo(bIntex);
          },
        );

which returns

['ALL', 'FLUTTER', 'WELT', 'BILD', 'VIMN', 'DRIT'];

but actually, I want to have it like:

['WELT', 'BILD', 'VIMN', 'DRIT', 'ALL', 'FLUTTER']

could someone help me, please?
thanks in advance

>Solution :

First thing, indexOf returns -1 when the element is not in the list, therefore it will put those in front. A solution for that is to change it to a higher number in that case.
Secondly, you also need to sort them alphabetically, which you don’t do now. You can do that by doing a compareTo on the strings themselves in the case that the first compareTo returns 0.

final result:

loadedSummaryList.sort(
      (a, b) {
    int aIntex = sortList.indexOf(a);
    int bIntex = sortList.indexOf(b);
    if (aIntex == -1) aIntex = sortList.length;
    if (bIntex == -1) bIntex = sortList.length;
    var result = aIntex.compareTo(bIntex);
    if (result != 0) {
      return result;
    } else {
      return a.compareTo(b);
    }
  },
);