CODEWITHSUNDEEP
listmapsdart
Peter
Peter

Reputation: 1919

Lists AS value of a Map in Dart

I want to create a map of members, but every membres have 3 propreties : first name, last name, and username. How can I create like a list of liste, but with a map.

So I want to have something like : 

var membres= {['lastname': 'Bonneau',
              'firstname': 'Pierre',
              'username': 'mariobross'],
              ['lastname': 'Hamel',
               'firstname': 'Alex',
               'username': 'Queenlatifa'],
            };

As you know, this code doesn't work. But it explain pretty well what I am trying to do.

Upvotes: 1

Views: 3069

Answers (5)

Junaid Lodhi
Junaid Lodhi

Reputation: 361

First of all you need to create a map with value as list. Dont forget to initialize it then if you want to fill it you first need to use built in function like putIfAbsent as in dart to add first object in list and then use update to add items in list. therefore you will need two arrays. First to put elements and then to add elements in list with same key. Also you can use try catch to identify if the key is present or not to do that in one loop

for (var item in days) {
    var date_time = DateTime.parse(item["date"] + " 00:00:00");
    _events[date_time] = _events.putIfAbsent(
        date_time,
        () => [
              {
                "title": item["title"],
                "date": item["date"],
                "time": reUse.get_time_am_pm_format(item["time"]),
                "feature": item["feature"],
              }
            ]);
  }
  for (var item in days) {
    var date_time = DateTime.parse(item["date"] + " 00:00:00");
    _events[date_time] = _events.update(date_time, (value) {
      value.add({
        "title": item["title"],
        "date": item["date"],
        "time": reUse.get_time_am_pm_format(item["time"]),
        "feature": item["feature"],
      });
      return value;
    });
  }

Upvotes: 0

Kai Sellgren
Kai Sellgren

Reputation: 30212

I think you are confusing the two constructs here.

Read this introduction to the language: http://www.dartlang.org/docs/dart-up-and-running/ch02.html#lists

A list is a list of elements which can be denoted with the shorthand [...] syntax:

var list = [1, 2, "foo", 3, new Date.now(), 4];

Whereas a map can be denoted with the curly brace shorthand syntax:

var gifts = {                         // A map literal
// Keys       Values
  'first'  : 'partridge',
  'second' : 'turtledoves',
  'fifth'  : 'golden rings'
};

So, let's modify your code to work:

var members = [
  {
    'lastname': 'Bonneau',
    'firstname': 'Pierre',
    'username': 'mariobross'
  },
  {
    'lastname': 'Hamel',
    'firstname': 'Alex',
    'username': 'Queenlatifa'
  }
];

You can, for example, print the information like this:

members.forEach((e) {
  print(e['firstname']);
});

Upvotes: 3

Alexandre Ardhuin
Alexandre Ardhuin

Reputation: 76203

If you don't really need a Map, what about using a class to improve the structure of your code :

class Member {
  String firstname;
  String lastname;
  String username;
  Member(this.firstname, this.lastname, this.username);
}

main() {
  final members = new List<Member>();
  members.add(new Member('Pierre', 'Bonneau', 'mariobross'));
  members.add(new Member('Alex', 'Hamel', 'Queenlatifa'));
  // use members
}

Upvotes: 1

Ali Akbar
Ali Akbar

Reputation: 794

You mean like this?

// FirstName => LastName => Value
var lookup = new Map<String, Map<String, String>>();

// get / set values like this
void setValue(String firstName, String lastName, String value) {
   if (!lookUp.containsKey(firstName)) 
       lookUp[firstName] = new Map<String, String>();
   lookUp[firstName][lastName] = value;
}

String getValue(String firstName, String lastName) {
   if (!lookUp.containsKey(firstName)) return "";
   return lookUp[firstName][lastName];
}

Upvotes: 0

beatgammit
beatgammit

Reputation: 20215

If I understand your intent correctly, you want to have a list of maps. What you have is correct except you confused [ and {. The following works:

var membres = [
          {'lastname': 'Bonneau',
           'firstname': 'Pierre',
           'username': 'mariobross'},
          {'lastname': 'Hamel',
           'firstname': 'Alex',
           'username': 'Queenlatifa'}
        ];

As an example, to get a list of all usernames:

print(membres.map((v) => v['username']));

Upvotes: 2

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