CODEWITHSUNDEEP
listflutterdartinsert
Ropali Munshi
Ropali Munshi

Reputation: 3026

Insert element at the beginning of the list in dart

I am just creating a simple ToDo App in Flutter. I am managing all the todo tasks on the list. I want to add any new todo tasks at the beginning of the list. I am able to use this workaround kind of thing to achieve that. Is there any better way to do this?

void _addTodoInList(BuildContext context){
    String val = _textFieldController.text;

    final newTodo = {
      "title": val,
      "id": Uuid().v4(),
      "done": false
    };

    final copiedTodos = List.from(_todos);

    _todos.removeRange(0, _todos.length);
    setState(() {
      _todos.addAll([newTodo, ...copiedTodos]);
    });

    Navigator.pop(context);
  }

Upvotes: 144

Views: 105698

Answers (7)

Elmar
Elmar

Reputation: 4417

Adding a new item to the beginning and ending of the list:

List<String> myList = ["You", "Can", "Do", "It"];
myList.insert(0, "Sure"); // adding a new item to the beginning

// new list is: ["Sure", "You", "Can", "Do", "It"];

lastItemIndex = myList.length;

myList.insert(lastItemIndex, "Too"); // adding a new item to the ending
// new list is: ["You", "Can", "Do", "It", "Too"];

Upvotes: 11

Shoaib Khan
Shoaib Khan

Reputation: 1060

For those who are looking for an easy method to add multiple items at the start position you can use this reference:

List<int> _listOne = [4,5,6,7];
List<int> _listTwo = [1,2,3];

_listOne.insertAll(0, _listTwo);

Upvotes: 5

Dennis Mwea
Dennis Mwea

Reputation: 589

Better yet and in case you want to add more items :-

List<int> myList = <int>[1, 2, 3, 4, 5];
myList = <int>[-5, -4, -3, -2, -1, ...myList];

Upvotes: 4

nategurutech
nategurutech

Reputation: 371

The other answers are good, but now that Dart has something very similar to Python's list comprehension I'd like to note it.

// Given
List<int> list = [2, 3, 4];

list = [
  1,
  for (int item in list) item,
];

or

list = [
  1,
  ...list,
];

results in [1, 2, 3, 4]

Upvotes: 7

Nikhil Biju
Nikhil Biju

Reputation: 825

I would like to add another way to attach element at the start of a list like this

 var list=[1,2,3];
 var a=0;
 list=[a,...list];
 print(list);

//prints [0, 1, 2, 3]

Upvotes: 17

Abdelrahman Lotfy
Abdelrahman Lotfy

Reputation: 361

Use

List.insert(index, value);

Upvotes: 36

CopsOnRoad
CopsOnRoad

Reputation: 267784

Use insert() method of List to add the item, here the index would be 0 to add it in the beginning. Example: 

List<String> list = ["B", "C", "D"];
list.insert(0, "A"); // at index 0 we are adding A
// list now becomes ["A", "B", "C", "D"]

Upvotes: 284

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