remove duplicates in json in flutter

To remove duplicates in a JSON array in Flutter, you can follow these steps:

1. Parse the JSON string into a list of objects using the json.decode() method.
2. Convert the list into a Set to remove duplicates.
3. Convert the Set back into a list using the toList() method.
4. Encode the list back into a JSON string using the json.encode() method.

Here's an example code snippet that demonstrates this process:

import 'dart:convert';

void main() {
  String jsonString = '[{"id": 1, "name": "John"}, {"id": 2, "name": "Jane"}, {"id": 1, "name": "John"}]';

  List<dynamic> jsonList = json.decode(jsonString);
  List<dynamic> uniqueList = jsonList.toSet().toList();
  String uniqueJsonString = json.encode(uniqueList);

  print(uniqueJsonString);
}

In this example, the jsonString variable represents the JSON string with duplicates. The json.decode() method is used to parse the JSON string into a list of objects. The toSet() method is then used to convert the list into a Set, which automatically removes duplicates. Finally, the toList() method converts the Set back into a list, and the json.encode() method is used to encode the list back into a JSON string.

When you run this code, the output will be:

[{"id":1,"name":"John"},{"id":2,"name":"Jane"}]

This is the JSON string with duplicates removed.