Realm Objects¶

Live Object¶

Objects in Realm clients are live objects that update automatically to reflect data changes, including synced remote changes, and emit notification events that you can subscribe to whenever their underlying data changes. You can use live objects to work with object-oriented data natively without an ORM tool.

Live objects are direct proxies to the underlying stored data, which means that a live object doesn't directly contain data. Instead, a live object always references the most up-to-date data on disk and lazy loads property values when you access them from a collection. This means that a realm can contain many objects, but you only pay the performance cost for data that the application is actually using.

Valid write operations on a live object automatically persist to the realm and propagate to any other synced clients. You do not need to call an update method, modify the realm, or otherwise "push" updates.

Object Model¶

An object model is a configuration object that defines the fields and relationships of a Realm object type. Realm Swift and Objective-C client applications define object models as classes derived from Object in Swift or RLMObject in Objective-C.

Primary Key¶

A primary key is a String or ObjectId property that uniquely identifies an object. You may optionally define a primary key for an object type as part of the object model. Realm Database automatically indexes primary key properties, which allows you to efficiently read and modify objects based on their primary key.

If an object type has a primary key, then all instances of that type must include the primary key property with a value that is unique among objects of the same type in a realm. You cannot change the primary key property for an object type after any object of that type is added to a realm.

Specify your primary key to Realm by overriding the primaryKey method in your class and returning the name of the property:

class Person: Object {
    @objc dynamic var _id = ObjectId()
    @objc dynamic var name = ""
    let dogs = LinkingObjects(fromType: Dog.self, property: "owner")
    override static func primaryKey() -> String? {
        return "_id"
    }
}

Optional or Required Properties¶

class Person: Object {
    // Required string property
    @objc dynamic var name: String = ""
    // Optional string property
    @objc dynamic var address: String?
    // Optional integral type property
    let age = RealmOptional<Int>()
}