Define a Realm Object Schema - Flutter SDK

Create Model

part 'schemas.g.dart';

@RealmModel()
class _Car {
  @PrimaryKey()
  late ObjectId id;
  late String make;
  late String? model;
  late int? miles;
}

.
├── schemas.dart
├── schemas.g.dart // newly generated file
├── myapp.dart
└── ...rest of application

import './schemas.dart';
final hondaCivic = Car(ObjectId(), 'Honda', model: 'Civic', miles: 99);

Using Schemas with Device Sync

An App Services Schema is a list of valid object schemas that each define an object type that an App may persist. All synced objects in a realm must conform to the App Services Schema.

Client applications provide a Object Schema when they open a realm. If a realm already contains data, then it already has a schema, and when it is opened, Realm Database validates the schema on the client against the existing schema.

You can define App Services Schemas in the following ways:

• Automatically with the Object Schema if development mode is enabled.

• Explicitly define the App Services Schema with App Services.

In your schema you must use the MapTo("_id") annotation with your primary key in the RealmModel to successfully sync your Object Schema with App Services.

@RealmModel()
class _SyncSchema {
  @PrimaryKey()
  @MapTo("_id")
  late ObjectId id;
  // ... other properties
}

For further information on defining your schema and which of these approaches you should consider for your application, refer to the Create a Realm Schema documentation.

Supported Data Types

Realm schemas support many Dart-language data types, in addition to some Realm-specific types. For a comprehensive reference of all supported data types, refer to Data Types.

Property Annotations

Use annotations to add functionality to properties in your Realm object models. You can use annotations for things like marking a property as nullable, setting a primary key, ignoring a property, and more. To learn more about the available property annotations, refer to Property Annotations.

Define Relationship Properties

You can define relationships between Realm objects in your schema. The Realm Flutter SDK supports to-one relationships, to-many relationships, inverse relationships, and embedding objects within other objects. To learn more about how to define relationships in your Realm object schema, refer to Relationships.

Map Realm Model to Different Name

You can use the MapTo annotation to map a Realm object model to a different model name in Realm Database. This can be useful in the following scenarios:

• Working with one realm from different Realm SDKs

• Migrating Realm object models

• Adhering to certain code style conventions

If you're using Atlas Device Sync, the name that you map to corresponds with the App Services Schema name.

@RealmModel()
@MapTo('naval_ship')
class _Boat {
  @PrimaryKey()
  late ObjectId id;
  late String name;
  late int? maxKnots;
  late int? nauticalMiles;
}

Generate the RealmObject

Once you've completed your Realm model, you must generate the RealmObject class to use it in your application.

Run the following command to generate RealmObjects:

Running this creates a public class in a new file in the directory where you defined the RealmModel class per the Create Model section.

The generated file has the same base name as the file with your RealmModel, ending with .g.dart. For example if the file with your RealmModel is named schemas.dart, the generated file will be schemas.g.dart.

// ...import packages
part 'schemas.g.dart';
@RealmModel()
// ...model definition

If you'd like to watch your data models to generate RealmObjects whenever there's a change, include the --watch flag in your command.

To clean the generator caches, include the --clean flag in your command. Cleaning the generator cache can be useful when debugging.