CODEWITHSUNDEEP
flutterdictionarydart
rmarquet21
rmarquet21

Reputation: 144

How to transform List into Map of List

I have a list with this data and I want to transform this in a Map<DateTime, List> with as variable for event (_id, title, date, active), ere is an example of data that I recover:

[
   {
      "_id":8,
      "title":"Matin",
      "date":"2021-08-04T00:00:00.000Z",
      "active":1
   },
   {
      "_id":9,
      "title":"Après-midi",
      "date":"2021-08-04T12:00:00.000Z",
      "active":1
   },
   {
      "_id":11,
      "title":"Matin",
      "date":"2021-08-05T00:00:00.000Z",
      "active":1
   },
   {
      "_id":12,
      "title":"Après-midi",
      "date":"2021-08-05T12:00:00.000Z",
      "active":1
   },
   {
      "_id":6,
      "title":"Matin",
      "date":"2021-08-11T00:00:00.000Z",
      "active":1
   },
   {
      "_id":7,
      "title":"Après-midi",
      "date":"2021-08-11T12:00:00.000Z",
      "active":1
   },
   {
      "_id":4,
      "title":"Matin",
      "date":"2021-08-17T00:00:00.000Z",
      "active":1
   },
   {
      "_id":10,
      "title":"Matin",
      "date":"2021-08-17T00:00:00.000Z",
      "active":1
   }
]

And in each value I have a date with year, month, day and time and I would like to group the dates without taking the hour into account, what will look like this:

"2021-08-04": [
{
      "_id":8,
      "title":"Matin",
      "date":"2021-08-04T00:00:00.000Z",
      "active":1
   },
   {
      "_id":9,
      "title":"Après-midi",
      "date":"2021-08-04T12:00:00.000Z",
      "active":1
   }
],
"2021-08-05": [
[
   {
      "_id":11,
      "title":"Matin",
      "date":"2021-08-05T00:00:00.000Z",
      "active":1
   },
   {
      "_id":12,
      "title":"Après-midi",
      "date":"2021-08-05T12:00:00.000Z",
      "active":1
   }
]

I try to do something with Map.fromIterable but I have some error... If someone can help me thanks !

Upvotes: 1

Views: 183

Answers (3)

venir
venir

Reputation: 2096

Considering that data is the List<Map<String, Object>> variable you listed, i.e. assuming your data is not a JSON object, I'd do:

Map<String, List<Map<String,Object>>> myTfData = {}
data.forEach(
    (value) {
      var myDate = value['date'] as String;
      if(myTfData.containsKey(myDate)) myTfData[myDate] = [];
      myTfData[myDate]!.add(value);
    }
  );

You'd obtain a Map<String, List<Map<String,Object>>> object as requested.

Upvotes: 1

Siqlain Hanif
Siqlain Hanif

Reputation: 31

As you are using flutter there is a package that can handle this of stuff. https://pub.dev/packages/collection

you will need groupby.

i did something like that, idk if the api is still the same. Anyhow here is the snippet.

.map(
        (List<Appointment> appointments) {
          appointments.sort(
            (Appointment a, Appointment b) {
              if (a.appointmentdate
                  .difference(b.appointmentdate)
                  .isNegative) return -1;
              return 1;
            },
          );
          return appointments;
        },
      ).distinct();

Upvotes: 1

Nagulan S
Nagulan S

Reputation: 752

I brute-forced the solution type you need. The provided solution will work for sure if the format of the date stored doesn't change.

void converter(var data) {
  var req={};
  for (int i = 0; i < data.length; i++) {
    var date=data[i]["date"].toString().substring(0,10);
    if(!req.containsKey(date))
      req[date]=[];
    req[date].add(data[i]);
  }
  print(req);
}

Upvotes: 1

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