Flutter/Dart how to groupBy list of maps

Question

I have this list of maps.

[
    {title: \'Avengers\', release_date: \'10/01/2019\'},
    {title: \'Creed\', release_date: \'10/01/2019\'}
    {title: \'Juman         


        

Answer 1

This is a method naively implemented (in case you don't want to use the groupBy function from the collections package):

List>>> MapByKey(String keyName, String newKeyName, String keyForNewName, List> input) {
  Map>>> returnValue = Map>>>();
  for (var currMap in input) {
    if (currMap.containsKey(keyName)) {
      var currKeyValue = currMap[keyName];
      var currKeyValueForNewName = currMap[keyForNewName];
      if (!returnValue.containsKey(currKeyValue)){
        returnValue[currKeyValue] = {currKeyValue : List>()};  
      }
      returnValue[currKeyValue][currKeyValue].add({newKeyName : currKeyValueForNewName});
    }
  }
  return returnValue.values.toList();
}

void main() {
    var test = [
    {"title": 'Avengers', "release_date": '10/01/2019'},
    {"title": 'Creed', "release_date": '10/01/2019'},
    {"title": 'Jumanji', "release_date": '30/10/2019'},
  ];

  var testMapped = MapByKey("release_date", "name", "title", test);

  print("$testMapped");
}

The output is:

[
    {
        10/01/2019: [
            {name: Avengers
            },
            {name: Creed
            }
        ]
    },
    {
        30/10/2019: [
            {name: Jumanji
            }
        ]
    }
]