在 dart 中不可能有 Map 个列表吗？

Question

I have data in this order:-

m={ 1:[54,23,98],
    9:[8,4,2]
   }

I'm trying to achieve something like this using the following code but it's not working. Where am I going wrong? Is there another way of storing and accessing this type of data in dart if my method is completely wrong?

Map<int,List<int>> m;

 m[0]=[];
 m[0].add(5);

Answer 1

You have to initialise it with empty map first

  Map<int, List<int>> m={}; //<- initialise it here
  m[0] = [];
  m[0].add(5);
  print(m); // prints {0: [5]}