How to create a matrix in Dart?

Question

I have a List<String> and I want to create a square matrix (2-dimensional array/list) of Set<String> with the same dimensions as the length of the List<String>.

I tried using

List.filled(entries.length, List.filled(entries.length, Set<String>()));

but the problem is that it seems that each row of my matrix refers to the same list instance, so changing a value in one row changes it in all the others as well.

So then I tried

List.filled(entries.length, List.from(List.filled(entries.length, Set<String>())));

but I still have the same problem. Eventually I surrendered and resorted to

List<List<Set<String>>> matrix = [];

for(int i=0; i<entries.length; i++) {
    List<Set<String>> row = [];
    for (int n = 0; n<entries.length; n++) {
        row.add(Set<String>());
    }
    matrix.add(row);
}

It works, but it's ugly. Is there a cleaner way to do this?

Solution

List.generate(n, (_) => List.generate(n, (_) => <String>{}));

Comments

[lrn]

With the new list literal syntax, you can even do: List<List<Set<String>>> matrix = [for (var _ in entries) [ for (var _ in entries) {} ]]; or ... = [for (int i = 0; i < n; i++) [ for (var j = 0; j < n; j++) {}]];.