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Flutter – Searching or removing a list from multi dimensional list in dart

Recently was working with dart multi-dimensional list, i have tried to remove a row(list) from a 2 dimensional list but the remove has no effect neither contains method has a match.

 List<List<int>> list = [[1, 2], [3, 4]];
 print(list.contains([1,2])); // prints false also removing will not has an effect

while

 List<List<int>> list = [[1, 2], [3, 4]];
 print(list.contains(list[0])); // prints true and successful remove

Why passing a list doesn’t have a match, I know that comparison here is based on reference not the value, but shouldn’t lists be canonicalized just like String and other numerical data types.

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2

Answers


  1. 0

    It seems correct,[1，2] != list[0].
    you can see the implement of the contains function:

     bool contains(Object? element) {
    for (E e in this) {
      if (e == element) return true;
    }
    return false;
  }

    In your case,you can use listEquals such as :

    list.retainWhere((item) => !listEquals(item, [1, 2]));
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  2. 0

    You can use listEqual() to compare list

    var list = [
  [1, 2],
  [3, 4]
];
list.removeWhere(
  (element) {
    return listEquals(element, [1, 2]);
  },
);

    Output

    [log]  [[3, 4]]
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