How to generate unique id in Dart

Question

I write websocket chat. How to generate unique id for user?

now i use this code:

id = new DateTime.now().millisecondsSinceEpoch;

is there any more neat solution?

Answer 1

1. There is a UUID pub package:

http://pub.dartlang.org/packages/uuid

example usage:

import 'package:uuid/uuid.dart';

// Create uuid object
var uuid = Uuid();

// Generate a v1 (time-based) id
uuid.v1(); // -> '6c84fb90-12c4-11e1-840d-7b25c5ee775a'

// Generate a v4 (random) id
uuid.v4(); // -> '110ec58a-a0f2-4ac4-8393-c866d813b8d1'

// Generate a v5 (namespace-name-sha1-based) id
uuid.v5(uuid.NAMESPACE_URL, 'www.google.com'); // -> 'c74a196f-f19d-5ea9-bffd-a2742432fc9c'

2. This src has a dart GUID generator

https://github.com/MikeMitterer/AndroidIconGenerator.DART/blob/445884924/lib/src/model/communication/GUIDGen.dart

I'll not post the function src here directly as there is no apparent licence with it, but example usage is as follows:

final String uuid = GUIDGen.generate();

Answer 2

In year 2020 you can do UniqueKey(); which is a built in class:

https://api.flutter.dev/flutter/foundation/UniqueKey-class.html

Note

A key that is only equal to itself.

This cannot be created with a const constructor because that implies that all instantiated keys would be the same instance and therefore not be unique.

Answer 3

I use microseconds instead of milliseconds, which is much more accurate and there is no need to add any package.

 String idGenerator() {
    final now = DateTime.now();
    return now.microsecondsSinceEpoch.toString();
  }

Answer 4

Besides from uuid, you can also try this to generate small unique keys:

https://pub.dev/packages/nanoid

They even have a collision calculator:

https://zelark.github.io/nano-id-cc/

Answer 5

This method will generate unique Id similar to (-N4pvg_50j1CEqSb3SZt)

String getCustomUniqueId() {
  const String pushChars =
      '-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';
  int lastPushTime = 0;
  List lastRandChars = [];
  int now = DateTime.now().millisecondsSinceEpoch;
  bool duplicateTime = (now == lastPushTime);
  lastPushTime = now;
  List timeStampChars = List<String>.filled(8, '0');
  for (int i = 7; i >= 0; i--) {
    timeStampChars[i] = pushChars[now % 64];
    now = (now / 64).floor();
  }
  if (now != 0) {
    print("Id should be unique");
  }
  String uniqueId = timeStampChars.join('');
  if (!duplicateTime) {
    for (int i = 0; i < 12; i++) {
      lastRandChars.add((Random().nextDouble() * 64).floor());
    }
  } else {
    int i = 0;
    for (int i = 11; i >= 0 && lastRandChars[i] == 63; i--) {
      lastRandChars[i] = 0;
    }
    lastRandChars[i]++;
  }
  for (int i = 0; i < 12; i++) {
    uniqueId += pushChars[lastRandChars[i]];
  }
  return uniqueId;
}

Answer 6

I've built a scenario to generate a unique cryptographically secure random id. with 4 random generations id's

1. First 4 Alphabets from an alphabets list [a-z].

2. Middle 4 digits from a digits list [0-9].

3. DateTime 4 microseconds since epoch substring 8 - 12 because they change frequently.

4. Last 4 Alphabets from an alphabets list [a-z].

Screen Shots of Generated id's:

A Function to Call

  randomIdGenerator() {
  var ranAssets = RanKeyAssets();
  String first4alphabets = '';
  String middle4Digits = '';
  String last4alphabets = '';
  for (int i = 0; i < 4; i++) {
    first4alphabets += ranAssets.smallAlphabets[
        math.Random.secure().nextInt(ranAssets.smallAlphabets.length)];

    middle4Digits +=
        ranAssets.digits[math.Random.secure().nextInt(ranAssets.digits.length)];

    last4alphabets += ranAssets.smallAlphabets[
        math.Random.secure().nextInt(ranAssets.smallAlphabets.length)];
  }

  return '$first4alphabets-$middle4Digits-${DateTime.now().microsecondsSinceEpoch.toString().substring(8, 12)}-$last4alphabets';
}

Class for list

    class RanKeyAssets {
  var smallAlphabets = [
    'a',
    'b',
    'c',
    'd',
    'e',
    'f',
    'g',
    'h',
    'i',
    'j',
    'k',
    'l',
    'm',
    'n',
    'o',
    'p',
    'q',
    'r',
    's',
    't',
    'u',
    'v',
    'w',
    'x',
    'y',
    'z'
  ];
  var digits = [
    '0',
    '1',
    '2',
    '3',
    '4',
    '5',
    '6',
    '7',
    '8',
    '9',
  ];
}

Answer 7

If you like MongoDB style ids you could consider this small package that will help create the object id:

https://pub.dev/packages/crossplat_objectid

import 'package:bson_objectid/bson_objectid.dart';

main() {
  ObjectId id1 = new ObjectId();
  print(id1.toHexString());

  ObjectId id2 = new ObjectId.fromHexString('54495ad94c934721ede76d90');
  print(id2.timestamp);
  print(id2.machineId);
  print(id2.processId);
  print(id2.counter);
}

Answer 8

There is also https://pub.dev/packages/xid which is lock free and has a Unicity guaranteed for 16,777,216 (24 bits) unique ids per second and per host/process

import 'package:xid/xid.dart';

void main() {
  var xid = Xid();
  print('generated id: $xid');

}