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Tito Soft
Asked: 2022-02-13 08:27:05 +0800 CST 2022-02-13 08:27:05 +0800 CST

Create a Map from another Map in dart or flutter

  • 772

Good day.

Check, I have a

lista = {"A" : 100, "B" : 80, "C": 70, "D": 60, "E": 50, "F": 30}

What I want is to get a Mapwith the first 3 elements:

listaFinal = {"A" : 100, "B" : 80, "C": 70}

Can I only create mi listaFinal by making a to it foror is there another way to get the listaFinal ?

Additionally, there will be some way to add its elements without doing an forelement loop x.

I mean, get something like this

MapFinal2 = {"A" : 100, "B" : 80, "C": 70, "OTROS": 140}

Where "OTHERS" has the sum of "E", "F" and "G"

This code I am using to add:

var sum = lista.entries
  //.where((e) => e.key.startsWith('A'))
  .map<int>((e) => e.value)
  .reduce((a, b) => a + b);

But in the Where I don't know what to put so that I only add the first 3 or 4 elements of the Map. Additionally I would like to cut my first map and get only the first 3.

Thank you

flutter

1 Answers

  1. Best Answer

    For the first case:

    
    final map = {"A": 100, "B": 80, "C": 70, "D": 60, "E": 50, "F": 30}
      ..removeWhere((key, value) => key.compareTo("C") > 0);
    print(map);

    For the second case, as I mentioned, a simple for has O(n) complexity, so it doesn't affect anything.

        final map2 = {"A": 100, "B": 80, "C": 70, "D": 60, "E": 50, "F": 30};

    int sum = 0;
    for (String key in Map.from(map2).keys) {
      if (key.compareTo("C") > 0) {
        sum += map2[key];
        map2.remove(key);
      }
    }
    map2["OTROS"] = sum;
    print(map2);
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