ObjectBox for Dart/Flutter

ObjectBox for Dart is a standalone database storing Dart objects locally, with strong ACID semantics.

Flutter/Dart compatibility

This library depends on a new Dart feature, FFI, introduced in Dart 2.5 (Flutter 1.9) as a feature preview. However, it has changed significantly in Dart 2.6/Flutter 1.12, i.e. introduced breaking changes we had to reflect. Versions starting with ObjectBox 0.5 support Dart 2.6+ as well as Flutter 1.12+.

The last supported version for Flutter 1.9/Dart 2.5 is ObjectBox 0.4.*, so if you can't upgrade yet, please use the latest 0.4.x version instead.


Add the following dependencies to your pubspec.yaml:

  objectbox: ^0.6.4

  build_runner: ^1.0.0
  objectbox_generator: ^0.6.4

Proceed based on whether you're developing a Flutter app or a standalone dart program:

  1. Flutter only steps:
    • Install the packages flutter pub get
  2. Dart standalone programs:
    • Install the packages pub get
    • Install objectbox-c system-wide:
      • macOS/Linux: execute the following command (answer Y when it asks about installing to /usr/lib)
           bash <(curl -s https://raw.githubusercontent.com/objectbox/objectbox-dart/master/install.sh)
      • macOS: if dart later complains that it cannot find the libobjectbox.dylib you probably have to unsign the dart binary (source: dart issue):
           sudo codesign --remove-signature $(which dart)
      • Windows: use "Git Bash" or similar to execute the following command
           bash <(curl -s https://raw.githubusercontent.com/objectbox/objectbox-dart/master/install.sh)
        Then copy the downloaded lib/objectbox.dll to C:\Windows\System32\ (requires admin privileges).

ObjectBox generates code binding code for classes you want stored based using build_runner. After you've defined your persisted entities (see below), run pub run build_runner build or flutter pub run build_runner build.

Getting started

In general, Dart class annotations are used to mark classes as ObjectBox entities and provide meta information. Entity IDs and UIDs that are defined in their respective annotations need to be unique across all entities, while property IDs only need to be unique in their respective entity; property UIDs also need to be globally unique.

Each entity is required to have an ID property of type int. Already persisted entities have an ID greater or equal to 1. New (not yet persisted) objects typically have ID value of 0 or null: calling Box.put automatically assigns a new ID to the object.


For a code example, see example/README.md


Box is your main interface for storing and retrieving data.

var box = Box<Note>(store);
var note = Note(text: "Hello");
note.id = box.put(note);
print("new note got id ${note.id}");
print("refetched note: ${box.get(note.id)}");

Query and QueryBuilder

Basic querying can be done with e.g.:

// var store ...
// var box ...

box.putMany([Note(), Note(), Note()]);
box.put(Note.construct("Hello world!"));

final queryNullText = box.query(Note_.text.isNull()).build();

assert(queryNullText.count() == 3);

queryNullText.close(); // We have to manually close queries and query builders.

More complex queries can be constructed using and/or operators. Also there is basic operator overloading support for greater, less, and and or, respectively >, <, &, |.

// final box ...


// equivalent to

final overloaded = (value > 10) | date.isNull();
box.query(overloaded as Condition).build(); // the cast is necessary due to the type analyzer


The results from a query can be ordered using the order method, e.g.

final q = box.query(Entity_.number > 0)

// ...

final qt = box.query(Entity_.text.notNull())
  .order(Entity_.text, flags: Order.descending | Order.caseSensitive)

Help wanted

ObjectBox for Dart is still in an early stage with limited feature set (compared to other languages). To bring all these features to Dart, we're asking the community to help out. PRs are more than welcome! The ObjectBox team will try its best to guide you and answer questions.


Also, please let us know your feedback by opening an issue: for example, if you experience errors or if you have ideas for how to improve the API. Thanks!


Q: After adding ObjectBox, the size of the APK increased significantly. Why is that?
A: Flutter compresses its native libraries (.so files) by default in the APK. ObjectBox instructs the Android build to use uncompressed native libraries instead (following the official Android recommendations). This setting affects the Flutter native libraries as well. Thus the now uncompressed Flutter libraries add to the APK size as well; we've seen an additional 19 MB for the standard Flutter libraries. This is bad, right? Nope, actually uncompressed libraries use less storage space on device and have other advantages. For details, please review the official Android recommendations and the ObjectBox FAQ entry on this. Both links also explain how to force compression using android:extractNativeLibs="true".

See also


Copyright 2020 ObjectBox Ltd. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
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