floor 0.9.0

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Floor #

A supportive SQLite abstraction for your Flutter applications.

The Floor library provides a lightweight SQLite abstraction with automatic mapping between in-memory objects and database rows while still offering full control of the database with the use of SQL.

It's important to note that this library is not a full-featured ORM like Hibernate and will never be. Thus not supporting automatic relationship mapping is intentional.

This package is still in an early phase and the API will likely change.

pub package Build Status codecov

Table of contents #

  1. How to use this library
  2. Architecture
  3. Querying
  4. Persisting Data Changes
  5. Streams
  6. Transactions
  7. Entities
  8. Foreign Keys
  9. Primary Keys
  10. Indices
  11. Migrations
  12. In-Memory Database
  13. Callback
  14. Examples
  15. Naming
  16. Bugs and Feedback
  17. License

How to use this library #

  1. Add the runtime dependency floor as well as the generator floor_generator to your pubspec.yaml. The third dependency is build_runner which has to be included as a dev dependency just like the generator.

    • floor holds all the code you are going to use in your application.

    • floor_generator includes the code for generating the database classes.

    • build_runner enables a concrete way of generating source code files.

         sdk: flutter
       floor: ^0.9.0
       floor_generator: ^0.9.0
       build_runner: ^1.7.1
  2. Creating an Entity

    It will represent a database table as well as the scaffold of your business object. @entity marks the class as a persistent class. It's required to add a primary key to your table. You can do so by adding the @primaryKey annotation to an int property. There is no restriction on where you put the file containing the entity.

     // entity/person.dart
     import 'package:floor/floor.dart';
     class Person {
       final int id;
       final String name;
       Person(this.id, this.name);
  3. Creating a DAO

    This component is responsible for managing access to the underlying SQLite database. The abstract class contains the method signatures for querying the database which have to return a Future.

    • You can define queries by adding the @Query annotation to a method. The SQL statement has to get added in parenthesis. The method must return a Future of the Entity you're querying for.

    • @insert marks a method as an insertion method.

     // dao/person_dao.dart   
     import 'package:floor/floor.dart';
     abstract class PersonDao {
       @Query('SELECT * FROM Person')
       Future<List<Person>> findAllPersons();
       @Query('SELECT * FROM Person WHERE id = :id')
       Future<Person> findPersonById(int id);
       Future<void> insertPerson(Person person);
  4. Creating the Database

    It has to be an abstract class which extends FloorDatabase. Furthermore, it's required to add @Database() to the signature of the class. Make sure to add the created entity to the entities attribute of the @Database annotation.

    In order to make the generated code work, it's required to also add the listed imports.

     // database.dart
     // required package imports
     import 'dart:async';
     import 'package:floor/floor.dart';
     import 'package:path/path.dart';
     import 'package:sqflite/sqflite.dart' as sqflite;   
     import 'dao/person_dao.dart';
     import 'model/person.dart';   
     part 'database.g.dart'; // the generated code will be there
     @Database(version: 1, entities: [Person])
     abstract class AppDatabase extends FloorDatabase {
       PersonDao get personDao;
  5. Make sure to add part 'database.g.dart'; beneath the imports of this file. It's important to note, that 'database' has to get exchanged with the name of the file the entity and database is defined in. In this case, the file is named database.dart.

  6. Run the generator with flutter packages pub run build_runner build. To automatically run it, whenever a file changes, use flutter packages pub run build_runner watch.

  7. Use the generated code. For obtaining an instance of the database, use the generated $FloorAppDatabase class, which allows access to a database builder. The name is composited from $Floor and the database class name. The string passed to databaseBuilder() will be the database file name. For initializing the database, call build().

     final database = await $FloorAppDatabase.databaseBuilder('app_database.db').build();
     final person = await database.findPersonById(1);
     await database.insertPerson(person);

For further examples take a look at the example and floor_test directories.

Architecture #

The components for storing and accessing data are Entity, Data Access Object (DAO) and Database.

The first, Entity, represents a persistent class and thus a database table. DAOs manage the access to Entities and take care of the mapping between in-memory objects and table rows. Lastly, Database, is the central access point to the underlying SQLite database. It holds the DAOs and, beyond that, takes care of initializing the database and its schema. Room serves as the source of inspiration for this composition, because it allows creating a clean separation of the component's responsibilities.

The figure shows the relationship between Entity, DAO and Database.

Floor Architecture

Querying #

Method signatures turn into query methods by adding the @Query() annotation with the query in parenthesis to them. Be patient about the correctness of your SQL statements. They are only partly validated while generating the code. These queries have to return either a Future or a Stream of an entity or void. Returning Future<void> comes in handy whenever you want to delete the full content of a table, for instance. Some query method examples can be seen in the following.

@Query('SELECT * FROM Person WHERE id = :id')
Future<Person> findPersonById(int id);

@Query('SELECT * FROM Person WHERE id = :id AND name = :name')
Future<Person> findPersonByIdAndName(int id, String name);

@Query('SELECT * FROM Person')
Future<List<Person>> findAllPersons(); // select multiple items

@Query('SELECT * FROM Person')
Stream<List<Person>> findAllPersonsAsStream(); // stream return

@Query('DELETE FROM Person')
Future<void> deleteAllPersons(); // query without returning an entity

@Query('SELECT * FROM Person WHERE id IN (:ids)')
Future<List<Person>> findPersonsWithIds(List<int> ids); // query with IN clause

Query arguments, when using SQLite's LIKE operator, have to be supplied by the input of a method. It's not possible to define a pattern matching argument like %foo% in the query itself.

// dao
@Query('SELECT * FROM Person WHERE name LIKE :name')
Future<List<City>> findPersonsWithNamesLike(String name);

// usage
final name = '%foo%';
await dao.findPersonsWithNamesLike(name);

Persisting Data Changes #

Use the @insert, @update and @delete annotations for inserting and changing persistent data. All these methods accept single or multiple entity instances.

  • Insert

    @insert marks a method as an insertion method. When using the capitalized @Insert you can specify a conflict strategy. Else it just defaults to aborting the insert. These methods can return a Future of either void, int or List<int>.

    • void return nothing
    • int return primary key of inserted item
    • List<int> return primary keys of inserted items
  • Update

    @update marks a method as an update method. When using the capitalized @Update you can specify a conflict strategy. Else it just defaults to aborting the update. These methods can return a Future of either void or int.

    • void return nothing
    • int return number of changed rows
  • Delete

    @delete marks a method as a deletion method. These methods can return a Future of either void or int.

    • void return nothing
    • int return number of deleted rows
// examples of changing multiple items with return 

Future<List<int>> insertPersons(List<Person> person);

Future<int> updatePersons(List<Person> person);

Future<int> deletePersons(List<Person> person);

Streams #

As already mentioned, queries can not only return a value once when called but also a continuous stream of query results. The returned stream keeps you in sync with the changes happening to the database table. This feature plays really well with the StreamBuilder widget.

These methods return a broadcast stream. Thus, it can have multiple listeners.

// definition
@Query('SELECT * FROM Person')
Stream<List<Person>> findAllPersonsAsStream();

// usage
  stream: dao.findAllPersonsAsStream(),
  builder: (BuildContext context, AsyncSnapshot<List<Person>> snapshot) {
    // do something with the values here

Transactions #

Whenever you want to perform some operations in a transaction you have to add the @transaction annotation to the method. It's also required to add the async modifier. These methods can only return Future<void>.

Future<void> replacePersons(List<Person> persons) async {
  await deleteAllPersons();
  await insertPersons(persons);

Entities #

An entity is a persistent class. Floor automatically creates the mappings between the in-memory objects and database table rows. It's possible to supply custom metadata to Floor by adding optional values to the Entity annotation. It has the additional attribute of tableName which opens up the possibility to use a custom name for that specific entity instead of using the class name. foreignKeys allows adding foreign keys to the entity. More information on how to use these can be found in the Foreign Keys section. Indices are supported as well. They can be used by adding an Index to the indices value of the entity. For further information of these, please refer to the Indices section.

@PrimaryKey marks property of a class as the primary key column. This property has to be of type int. The value can be automatically generated by SQLite when autoGenerate is enabled. For more information about primary keys and especially compound primary keys, refer to the Primary Keys section.

@ColumnInfo enables custom mapping of single table columns. With the annotation, it's possible to give columns a custom name and define if the column is able to store null.

@Entity(tableName: 'person')
class Person {
  @PrimaryKey(autoGenerate: true)
  final int id;

  @ColumnInfo(name: 'custom_name', nullable: false)
  final String name;

  Person(this.id, this.name);

Primary Keys #

Whenever a compound primary key is required (e.g. n-m relationships), the syntax for setting the keys differs from the previously mentioned way of setting primary keys. Instead of annotating a field with @PrimaryKey, the @Entity annotation's primaryKey attribute is used. It accepts a list of column names that make up the compound primary key.

@Entity(primaryKeys: ['id', 'name'])
class Person {
  final int id;

  final String name;

  Person(this.id, this.name);

Foreign Keys #

Add a list of ForeignKeys to the Entity annotation of the referencing entity. childColumns define the columns of the current entity, whereas parentColumns define the columns of the parent entity. Foreign key actions can get triggered after defining them for the onUpdate and onDelete properties.

  tableName: 'dog',
  foreignKeys: [
      childColumns: ['owner_id'],
      parentColumns: ['id'],
      entity: Person,
class Dog {
  final int id;

  final String name;

  @ColumnInfo(name: 'owner_id')
  final int ownerId;

  Dog(this.id, this.name, this.ownerId);

Indices #

Indices help speeding up query, join and grouping operations. For more information on SQLite indices please refer to the official documentation. To create an index with floor, add a list of indices to the @Entity annotation. The example below shows how to create an index on the custom_name column of the entity.

The index, moreover, can be named by using its name attribute. To set an index to be unique, use the unique attribute.

@Entity(tableName: 'person', indices: [Index(value: ['custom_name'])])
class Person {
  final int id;

  @ColumnInfo(name: 'custom_name', nullable: false)
  final String name;

  Person(this.id, this.name);

Migrations #

Whenever are doing changes to your entities, you're required to also migrate the old data.

First, update your entity. Next, Increase the database version. Define a Migration which specifies a startVersion, an endVersion and a function that executes SQL to migrate the data. At last, use addMigrations() on the obtained database builder to add migrations. Don't forget to trigger the code generator again, to create the code for handling the new entity.

// update entity with new 'nickname' field
@Entity(tableName: 'person')
class Person {
  @PrimaryKey(autoGenerate: true)
  final int id;

  @ColumnInfo(name: 'custom_name', nullable: false)
  final String name;
  final String nickname;

  Person(this.id, this.name, this.nickname);

// bump up database version
@Database(version: 2)
abstract class AppDatabase extends FloorDatabase {
  PersonDao get personDao;

// create migration
final migration1to2 = Migration(1, 2, (database) {
  database.execute('ALTER TABLE person ADD COLUMN nickname TEXT');

final database = await $FloorAppDatabase

In-Memory Database #

To instantiate an in-memory database, use the static inMemoryDatabaseBuilder() method of the generated $FloorAppDatabase class instead of databaseBuilder().

final database = await $FloorAppDatabase.inMemoryDatabaseBuilder('app_database.db').build();

Callback #

In order to hook into Floor's database initialization process, Callback should be used. It allows the invocation of three separate callbacks which are triggered when the database has been

  • initialized for the first time (onCreate).
  • opened (onOpen).
  • upgraded (onUpgrade).

Each callback is optional.

Their usage can be seen in the following snippet.

final callback = Callback(
   onCreate: (database, version) { /* database has been created */ },
   onOpen: (database) { /* database has been opened */},
   onUpgrade: (database, startVersion, endVersion) { /* database has been upgraded */ },

final database = await $FloorAppDatabase

Examples #

For further examples take a look at the example and floor_test directories.

Naming #

Floor - the bottom layer of a Room.

Bugs and Feedback #

For bugs, questions and discussions please use the Github Issues.

License #

Copyright 2019 Vitus Ortner

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at


Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
See the License for the specific language governing permissions and
limitations under the License.

Changelog #

0.9.0 #

🐛 Bug Fixes #

  • Make IN clauses work with strings
  • Fix foreign key action string representation

0.8.0 #

Changes #

  • Update README with clear package import instructions

🚀 Features #

  • Introduce static 'to map' functions
  • Add optional callback functions when opening database

🐛 Bug Fixes #

  • Allow int and string (composite) primary keys

0.7.0 #

🐛 Bug Fixes #

  • Retain reactivity when using transactions

0.6.0 #

🚀 Features #

  • Add support for IN clauses in query statements
  • Enable compound primary keys

0.5.0 #

Changes #

  • Make tasks deletable in example app

🚀 Features #

  • Allow multiline string queries
  • Allow void-return queries with arguments

0.4.2 #

🐛 Bug Fixes #

  • Fix query parameter substitution regex

0.4.0 #

Changes #

  • Enable coverage report
  • Simplify type assertions and add tests

🚀 Features #

  • Allow more convenient database initialization

🐛 Bug Fixes #

  • Use query argument binding instead of manual binding

0.3.0 #

Changes #

  • Use TypeChecker for all annotations
  • Add publishing instructions
  • Remove unused annotation names
  • Simplify the mapping from an entity to a map
  • Fix database writer test
  • Make stream emit query result on subscription
  • Update example to use StreamBuilder
  • Update README

🐛 Bug Fixes #

  • Correct mapper instance name referenced by generated query methods
  • Fix adapter instances naming

0.2.0 #

Changes #

  • Add database adapters
  • Run floor Flutter tests
  • Move value objects to value_objects directory
  • Map source elements into value objects in processors
  • Use GeneratorForAnnotation and TypeChecker to verify annotations
  • Throw more specific errors on obfuscated database annotation

🚀 Features #

  • Add support for migrations
  • Add support for returning Streams as query result
  • Support accessing data from Data Access Objects
  • Add entity classes to database annotation
  • Add support for indices

0.1.0 #

🚀 Features #

  • Support conflict strategies when inserting and updating records
  • Add support for running queries that return void
  • Add support for foreign keys
  • Add parameter verification for query methods
  • Return deleted row count on delete
  • Return updated rows count on update
  • Return ID/s of inserted item/s
  • Add support for transactions
  • Add support for changing (insert, update, delete) lists
  • Support custom entity name
  • Enable NOT NULL columns
  • Enable custom column name mapping
  • Add delete methods code generation and fix update methods
  • Add update methods code generation
  • Add insert methods code generation
  • Add code generator for query methods
  • Code generation for database creation

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:

  floor: ^0.9.0

2. Install it

You can install packages from the command line:

with Flutter:

$ flutter pub get

Alternatively, your editor might support flutter pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:

import 'package:floor/floor.dart';
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Learn more about scoring.

We analyzed this package on Jan 16, 2020, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.7.0
  • pana: 0.13.4
  • Flutter: 1.12.13+hotfix.5

Maintenance suggestions

Maintain an example. (-10 points)

Create a short demo in the example/ directory to show how to use this package.

Common filename patterns include main.dart, example.dart, and floor.dart. Packages with multiple examples should provide example/README.md.

For more information see the pub package layout conventions.


Package Constraint Resolved Available
Direct dependencies
Dart SDK >=2.3.0-dev <3.0.0
floor_annotation ^0.4.0 0.4.0
flutter 0.0.0
meta ^1.1.6 1.1.8
path ^1.6.2 1.6.4
sqflite ^1.1.6+4 1.2.0
Transitive dependencies
collection 1.14.11 1.14.12
sky_engine 0.0.99
synchronized 2.1.1
typed_data 1.1.6
vector_math 2.0.8
Dev dependencies
mockito ^4.1.0