Configure & Open a Realm - Flutter SDK

Open a Local-Only Realm

To create a realm that only persists data locally, create a configuration with Configuration.local(). You must provide a list of schemas as an argument.

Pass the Configuration to the Realm constructor.

final config = Configuration.local([Car.schema]);
final realm = Realm(config);

You can now use that realm instance to work with objects in the database.

Open a Synced Realm

To open a realm that synchronizes data with Atlas using Device Sync, refer to Open a Synced Realm.

Open an In-Memory Realm

To create a realm that runs in memory without being persisted, create your Configuration with Configuration.inMemory(). You must provide a list of schemas as an argument. In-memory realms cannot also be read-only.

Pass the Configuration to the Realm constructor.

final config = Configuration.inMemory([Car.schema]);
final realm = Realm(config);

Open a Read-Only Realm

You can open an existing realm in read-only mode. To open a read-only realm, add readOnly: true to your Configuration object.

You can only open existing realms in read-only mode. If you try to write to a read-only realm, it throws an error.

final config = Configuration.local([Car.schema], isReadOnly: true);
final realm = Realm(config);

Set Custom FIFO Special Files

Set a value for Realm's FIFO special files location. Opening a realm creates a number of lightweight FIFO special files that coordinate access to the realm across threads and processes. If the realm file is in a location that doesn't allow for the creation of FIFO special files (such as FAT32 filesystems), then the realm cannot be opened. In this case, Realm needs a different location to store these files. Add fifoFilesFallbackPath: <Your Custom FIFO File Path> to your Configuration object.

This property is ignored if the directory for the realm file allows FIFO special files.

final config = Configuration.local([Car.schema],
    fifoFilesFallbackPath: "./fifo_folder");
final realm = Realm(config);

Add Initial Data to Realm

Use initialDataCallback() to invoke a callback function the first time that you open a realm. The function only executes the first time that the realm on the device. The realm instance passed to the callback function already has a write transaction open, so you do not need to wrap write operations in a Realm.write() transaction block. initialDataCallback can be useful for adding initial data to your application the first time that it is opened on a device.

void dataCb(Realm realm) {
  realm.add(Car(ObjectId(), 'Honda'));
}
final config =
    Configuration.local([Car.schema], initialDataCallback: dataCb);
final realm = Realm(config);
Car honda = realm.all<Car>()[0];

Customize Default Configuration

You can customize the default path where Realm stores database files and the default name given to database files.

Use the static Configuration.defaultRealmName and Configuration.defaultRealmPath to set default configuration for all realms opened within an application.

Configuration.defaultRealmName = "myRealmName.realm";
final customDefaultRealmPath = path.join(
    (await Directory.systemTemp.createTemp()).path,
    Configuration.defaultRealmName);
Configuration.defaultRealmPath = customDefaultRealmPath;
// Configurations used in the application will use these values
final config = Configuration.local([Car.schema]);
// The path is your system's temp directory
// with the file named 'myRealmName.realm'
print(config.path);

You can also check where realm stores the files by default using the static getter Configuration.defaultStoragePath. The value for this property varies depending on the platform you are using the SDK on and whether you are using the Dart or Flutter versions of Realm. Check the value of Configuration.defaultStoragePath in your application to see where realm files are stored in your environment.

final storagePath = Configuration.defaultStoragePath;
// See value in your application
print(storagePath);

Manage Schema Changes

For more information about managing schema changes when configuring a realm, refer to the Update a Realm Object Schema documentation.

Encrypt a Realm

You can encrypt your local realm to ensure data security. For more information, see Encrypt a Realm.

Compact a Realm

You can reduce the local realm file size to improve performance and manage file size in a resource-constrained environment. For more information, refer to Compact a Realm.