A versatile library which solves autocompletion in Dart/Flutter. It is based around a space-efficient implementation of Trie which uses variable-length lists. With this, serving auto-suggestions is both fast and no-hassle. Suggestions are also sorted by how often they've been entered and subsorted by recency of entry, for search-engine-like results.

Read more about Trie here.

A Brief Note

It takes time, effort, and mental power to keep this package updated, useful, and improving. If you used or are using the package, I'd appreciate it if you could spare a few dollars to help me continue development.



A usage example is provided below. Check the API Reference for detailed docs:

import 'dart:io'; // you don't need to import this, it just has the sleep method (which I use here).

import 'package:autotrie/autotrie.dart';

void main() {
  var engine = AutoComplete(engine: SortEngine.configMulti(Duration(seconds: 1), 15, 0.5, 0.5)); //You can also initialize with a starting databank.

  var interval = Duration(milliseconds: 1);

  engine.enter('more'); // Enter more thrice.

  engine.enter('moody'); // Enter moody twice.

  engine.enter('morose'); // Enter scattered words (with mo).

  engine.enter('sorose'); // Enter scattered words (without mo).

  engine.delete('morose'); // Delete morose.

  // Check if morose is deleted.
  print('Morose deletion check: ${!engine.contains('morose')}');

  // Check if engine is empty.
  print('Engine emptiness check: ${engine.isEmpty}');

  // Suggestions starting with 'mo'.
  // They've been ranked by frequency and recency. Since they're all so similar
  // in recency, frequency takes priority.
  print("'mo' suggestions: ${engine.suggest('mo')}");
  // Result: [more, moody, momentum, moment, morty]

  // Get all entries.
  // They've not been sorted.
  print('All entries: ${engine.allEntries}');
  // Result: [more, moody, sorty, sorose, momentum, moment, morty]

// Check the API Reference for the latest information and adv.
// methods from this class.


The AutoComplete constructor takes a SortEngine, which it uses to sort the result of the autocompletion operation. There are a few different modes it can operate in:

  • SortEngine.entriesOnly() -> AutoComplete results are only sorted by number of entries in the engine (High to Low)
  • SortEngine.msOnly() -> AutoComplete results are only sorted by how much time has passed since their last entry (Low to High)
  • SortEngine.simpleMulti() ->
    • Sorted using two logistic curves, one for ms and one for entries
      • The ms curve is set to use 3 years (a LOT) as the upper end of how far back entries could have been entered
      • The entries curve is set to use 30 entries as the max amount of entries
      • These values are highly arbitrary and not likely to fit your project; this mode is not recommended unless you are just playing around.
    • Takes two weights (one for recency and one for entries) which can be used to balance how heavily each factor should affect the final sorting.
  • SortEngine.configMulti() ->
    • Sorted using two logistic curves, one for ms and one for entries
      • The ms curve is balanced using a parameter (a Duration) for the max time since entry in this engine.
      • The entries curve is balanced using a parameter (an int) for the max amount of entries in this engine.
      • If you know approximately how old and how big this AutoComplete engine is, it is highly recommended that you use this mode.
    • Takes two weights (one for recency and one for entries) which can be used to balance how heavily each factor should affect the final sorting.

Note that all the recency sorting functionality has a granularity of one millisecond. If you add multiple elements to the tree within the span of a single millisecond, they are regarded as functionally equivalent in the recency metric.

Basic File Persistence

AutoComplete is natively capable of writing itself to and reading itself from a file. To do this, persist to a file using the persist method (it takes a File object): await engine.persist(myFile);

Then you can rebuild using AutoComplete.fromFile (it takes a File along with the mandatory SortEngine): var engine = AutoComplete.fromFile(file: myFile, engine: SortEngine.entriesOnly());

This persistence will preserve all the metadata (last insert, number of entries) in the table as well as the core data (the Strings themselves).

Hive Integration

  • Hive is a speedy, local, and key-value database for Dart/Flutter. Go check it out if you haven't already!
  • Hive integration is now available with autotrie:
    • Our way of integration uses extension methods.
    • Import Hive and AutoTrie, and create a normal Hive box using Hive.openBox('nameHere').
    • You can then call searchKeys(String prefix) and searchValues(String prefix) on that box to get auto-suggestions.
    • There is no sorting options: only entry-level sorting is available.

Features and bugs

Please file feature requests and bugs at the issue tracker.

This library and its contents are subject to the terms of the Mozilla Public License, v. 2.0.
© 2021 Aditya Kishore


AutoTrie exports a class for autocompletion based on a List of Strings.