CODEWITHSUNDEEP
listdartfluttermaps
Francesco Iapicca
Francesco Iapicca

Reputation: 2657

How can I use and store a list inside a map in dart?

Aye aye good people,

I need to be able to add and delete elements from a list stored inside a map;

I wrongly assumed that this:

 final Map<int,List<int>> _map = Map();
_map[1].add(1);
int _data=_map[1][0];

or this:

Map<int,List<int>> _map = Map<int,List<int>>();
List _list = List();
_list.add(1);
_map[1]=_list;
int _data=_map[1][0];

would work, but doesn't.

So... how does it work?

Thank you in advance,

Francesco

Upvotes: 0

Views: 2498

Answers (1)

Alexandre Ardhuin
Alexandre Ardhuin

Reputation: 76183

The first _map[1] tries to get the value in the map _map for the given key 1. But at this time _map is empty so it returns null.

To lazy initialize your map, you can do:

final Map<int,List<int>> _map = Map();
_map.putIfAbsent(1, () => <int>[]).add(1);
int _data=_map[1][0];

Upvotes: 2

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