Question 261042 in Flutter Question posted in
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The non-nullable local variable 'result' must be assigned before it can be used Flutter

I am taking Angela Yu’s Flutter and Dart course and it is very outdated and I am getting a lot of errors.

This is an async await demo and the syntax has changed since she made the course. I have tried several ways but can never get the same response to what Angela gets in her videos.

The issue is in the result variable in the task2() function. It needs for me to assign it a value for it to work but when I do I still dont get the same response as her.

I have tried putting late before the task 2 string result, assigning it a value of an empty string ” and marking it as nullable with a question mark after and none of these work. I have attached my code plus an image of the output Angela is getting.

Any help and advice would be greatly appreciated.

Thank you.
Angela Yu's code

My result

`void main() {
  performTasks();
}

void performTasks() async {
  task1();
  String task2Result = await task2();
  print(task2());
  task3(task2Result);
}

void task1() {
  String result = 'task 1 data';
  print('Task 1 complete');
}

Future<String> task2() async {
  Duration threeSeconds = Duration(seconds: 3);

  late String result;

  await Future.delayed(threeSeconds, () {
    result = 'task 2 data biatch';
    print('Task 2 complete');
  });

  return result;
}

void task3(String task2data) {
  String result = 'task 3 data';
  print('Task 3 complete with $task2data');
}`
Tags:

2

Answers


  1. 0

    I can not see the images but by reading your code I see you are missing await keyword before task2 like this print(await task2());

    since task2 is future you need to wait for the result.

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  2. 0

    To replicate the result shown on the course video, you would need to remove the print(task2()) line from your performTasks function. task2 is a Future so you will be printing the instance information instead of the Future result. Furthermore, that would call the task2 function again and make the ‘Task 2 complete’ message gets printed twice.

    The final code of your performTasks function should look like this:

    void performTasks() async {
  task1();
  String task2Result = await task2();
  task3(task2Result);
}
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