appwrite/docs/examples/1.2.x/server-dart/examples/functions/update-variable.md

import 'package:dart_appwrite/dart_appwrite.dart';

void main() { // Init SDK
  Client client = Client();
  Functions functions = Functions(client);

  client
    .setEndpoint('https://cloud.appwrite.io/v1') // Your API Endpoint
    .setProject('5df5acd0d48c2') // Your project ID
    .setKey('919c2d18fb5d4...a2ae413da83346ad2') // Your secret API key
  ;

  Future result = functions.updateVariable(
    functionId: '[FUNCTION_ID]',
    variableId: '[VARIABLE_ID]',
    key: '[KEY]',
  );

  result
    .then((response) {
      print(response);
    }).catchError((error) {
      print(error.response);
  });
}