How to generate random numbers without repetition in Flutter - flutter

Question

I need to generate random numbers to use them as index and i need the generated number to be within a range and cannot be repeated. Is there a predefined function in Flutter to do that or am i going to create my own function?

Answer 1

you can use the Random class and then use a Set because unlike List you don't need to do any extra checking for duplication as Set itself won't allow any duplicated element.
for example:
Set<int> setOfInts = Set();
setOfInts.add(Random().nextInt(max));

Answer 2

I think you could simply create a simple shuffled list of index and use removeLast() on it each time you need a new value.
var randomPicker = List<int>.generate(n, (i) => i + 1)..shuffle();
...
int random1 = randomPicker.removeLast();
int random2 = randomPicker.removeLast();
assert(random1 != random2);
Where n is your maximum index.

Answer 3

Use random from math library:
import 'dart:math';
Random random = new Random();
int random_number = random.nextInt(100); // from 0 up to 99
And if you want to change minimum number you can use below trick, it will select from 10 up to 99:
int randomNumber = random.nextInt(90) + 10;
If you need multiple you can add those numbers to list and check them if there is exist with contain, such as:
List<int> numberList=[];
Random random = new Random();
for (var i = 0; i == 10; i++){
int random_number = random.nextInt(100);
if (!numberList.contains(random_number)) {numberList.add(random_number);}
}

Answer 4

I tried using all the codes above but none solved my problem.
I created this and it worked for me:
class Utils {
static final _random = Random();
static final Set<int> _setOfInts = {};
static int randomUnique({required limit}) {
debugPrint("limit: $limit ---> ${_setOfInts.length} ${_setOfInts.toString()}");
int randomInt = _random.nextInt(limit) + 1;
if (_setOfInts.contains(randomInt)) {
return randomUnique(limit: limit);
} else {
_setOfInts.add(randomInt);
return randomInt;
}
}
}