CODEWITHSUNDEEP
listflutterdartobject
Joe
Joe

Reputation: 441

How to actually duplicate lists/objects in Dart/Flutter

I have a list of objects that hold some user input.

What I want to achieve: Duplicating the list before resetting the objects to their default values, so I don't lose the information.

The problem: No matter what I try, whenever I modify objects in list_1, the objects in list_2 are being modified as well; overwriting the data I want to keep that way.

Attempts at solving it:

I tried declaring the second lists in all kinds of ways:

list_2 = list_1;
list_2 = List.of(list_1);
list_2 = [...list_1);
list_2 = list_1.toList();

No luck. I then tried this:

list_2=[];
for (var i in list_1){
  list_2.add(i);}

Still, the same behaviour. If I modify a value of an object in list_1, the corresponding object in list_2 is changed as well.

I'm confused. Am I only creating new references to the objects, but not actually multiplying them? How would I go about changing that? Is something else going on? THANKS!

Upvotes: 1

Views: 2503

Answers (2)

Mohammed Abdallah
Mohammed Abdallah

Reputation: 286

this happen to me while aago with objects

I fixed it by converting the object to json format then asign the new object from the json data with the method from the model fromJson(json) that worked fine

in case of the list there is an easier way

main() {
 List<int> x = [1, 2];

 List<int> y = [];

 x.map((e) => y.add(e)).toList();

 print(x.toString()); //[1, 2]
 y[0]++;
 print(y.toString()); //[2, 2]
 print(x.toString()); //[1, 2]
}

Upvotes: 0

dartKnightRises
dartKnightRises

Reputation: 905

Try this one:

Created a demo list:

  List<Status> statuses = <Status>[
    Status(name: 'Confirmed', isCheck: true),
    Status(name: 'Cancelled', isCheck: true),
  ];
List<Status> otherStatuses = statuses.map((status)=>Status(name:status.name, isCheck:status.isCheck)).toList()

Upvotes: 1

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