How to remove empty values in dart list-CodePudding

I have list of lists of dynamics which contain empty values. when I filter the list where values are not empty I get blank space separated by comma.

main.dart

const List<List<dynamic>> items = [
  ['name', 'username', 'email', 'password'],
  ['admin', '', 'test@mail', 'fakepass'],
  ['', 'useritemname', '', 'hello'],
];

void main() {
  final al = items.where((element) => element != '' && element.length >= 4);
  for (var l in al) {
    print(l);
  }
}

Above code give below results:

[name, username, email, password]
[admin, , test@mail, fakepass]
[, useritemname, , hello]

i want to remove those commas (, , and ,)

CodePudding user response：

, is for separating item in list, but ,, means you have empty string in your list, you can remove ,, with this:

List<List<dynamic>> newList = [];
    for (var item in items) {
      List<String> tempList = [];
      for (var element in item) {
        if (element.isNotEmpty) {
          tempList.add(element);
        }
      }
      newList.add(tempList);
    }

shorter version(tanks to @pskink):

List<List<dynamic>> newList items.map((l) => l.where((i) => i.isNotEmpty).toList()).toList();

results:

    print('newList = $newList'); //[[name, username, email, password], [admin, test@mail, fakepass], [useritemname, hello]]
    print('items = $items'); // [[name, username, email, password], [admin, , test@mail, fakepass], [, useritemname, , hello]]

CodePudding user response：

Even though the code of the other answer works I strongly commend to use strict typing. If you had strict typing you could have avoid these semantic errors:

Have a look at this:

const List<List<String>> items = [
  ['name', 'username', 'email', 'password'],
  ['admin', '', 'test@mail', 'fakepass'],
  ['', 'useritemname', '', 'hello'],
];

void main() {

  List al = items
    .map((List<String> list) => list.where((String element) => element != '' && element.length >= 4).toList())
    .toList();
  print(al);
}

This generates the output you want:

[name, username, email, password]
[admin, test@mail, fakepass]
[useritemname, hello]