Classes

A 128-bit IEEE 754-2008 decimal floating point number.

This type is similar to Swift’s built-in Decimal type, but allocates bits differently, resulting in a different representable range. (NS)Decimal stores a significand of up to 38 digits long and an exponent from -128 to 127, while this type stores up to 34 digits of significand and an exponent from -6143 to 6144.

A 12-byte (probably) unique object identifier.

ObjectIds are similar to a GUID or a UUID, and can be used to uniquely identify objects without a centralized ID generator. An ObjectID consists of:

1. A 4 byte timestamp measuring the creation time of the ObjectId in seconds since the Unix epoch.
2. A 5 byte random value
3. A 3 byte counter, initialized to a random value.

ObjectIds are intended to be fast to generate. Sorting by an ObjectId field will typically result in the objects being sorted in creation order.

List is the container type in Realm used to define to-many relationships.

Like Swift’s Array, List is a generic type that is parameterized on the type it stores. This can be either an Object subclass or one of the following types: Bool, Int, Int8, Int16, Int32, Int64, Float, Double, String, Data, Date, Decimal128, and ObjectId (and their optional versions)

Unlike Swift’s native collections, Lists are reference types, and are only immutable if the Realm that manages them is opened as read-only.

Lists can be filtered and sorted with the same predicates as Results<Element>.

Properties of List type defined on Object subclasses must be declared as let and cannot be dynamic.

MutableSet is the container type in Realm used to define to-many relationships with distinct values as objects.

Like Swift’s Set, MutableSet is a generic type that is parameterized on the type it stores. This can be either an Object subclass or one of the following types: Bool, Int, Int8, Int16, Int32, Int64, Float, Double, String, Data, Date, Decimal128, and ObjectId (and their optional versions)

Unlike Swift’s native collections, MutableSets are reference types, and are only immutable if the Realm that manages them is opened as read-only.

MutableSet’s can be filtered and sorted with the same predicates as Results<Element>.

Properties of MutableSet type defined on Object subclasses must be declared as let and cannot be dynamic.

Map is a key-value storage container used to store supported Realm types.

Map is a generic type that is parameterized on the type it stores. This can be either an Object subclass or one of the following types: Bool, Int, Int8, Int16, Int32, Int64, Float, Double, String, Data, Date, Decimal128, and ObjectId (and their optional versions)

Map only supports String as a key.

Unlike Swift’s native collections, Maps is a reference types, and are only immutable if the Realm that manages them is opened as read-only.

A Map can be filtered and sorted with the same predicates as Results<Value>.

Properties of Map type defined on Object subclasses must be declared as let and cannot be dynamic.

A RealmOptional instance represents an optional value for types that can’t be directly declared as @objc in Swift, such as Int, Float, Double, and Bool.

To change the underlying value stored by a RealmOptional instance, mutate the instance’s value property.

A RealmProperty instance represents an polymorphic value for supported types.

To change the underlying value stored by a RealmProperty instance, mutate the instance’s value property.

Projection is a light weight model of the original Realm Object or EmbeddedObject. You can use Projection as a view model to minimize boilerplate.

Example of usage:

public class Person: Object {
    @Persisted var firstName = ""
    @Persisted var lastName = ""
    @Persisted var address: Address? = nil
    @Persisted var friends = List<Person>()
    @Persisted var reviews = List<String>()
}

public class Address: EmbeddedObject {
    @Persisted var city: String = ""
    @Persisted var country = ""
}

class PersonProjection: Projection<Person> {
    @Projected(\Person.firstName) var firstName
    @Projected(\Person.lastName.localizedUppercase)
    var lastNameCaps
    @Projected(\Person.address.city) var homeCity
    @Projected(\Person.friends.projectTo.firstName)
    var friendsFirstName: ProjectedCollection<String>
}

### Supported property types

Projection can transform the original @Persisted properties in several ways:

• Passthrough - Projection‘s property will have same name and type as original object. See PersonProjection.firstName.
• Rename - Projection’s property will have same type as original object just with the new name.
• Keypath resolution - you can access the certain properties of the projected Object. See PersonProjection.lastNameCaps and PersonProjection.homeCity.
• Collection mapping - List and MutableSetof Objects or EmbeddedObjects can be projected as a collection of primitive values. See PersonProjection.friendsFirstName.
• Exclusion - all properties of the original Realm object that were not defined in the projection model will be excluded from projection. Any changes happened on those properties will not trigger a change notification for the Projection. You still can access the original Object or EmbeddedObject and observe notifications directly on it.

Querying

You can retrieve all Projections of a given type from a Realm by calling the objects(_:) of Realm or init(projecting:) of Projection’s class:

let projections = realm.object(PersonProjection.self)
let personObject = realm.create(Person.self)
let singleProjection = PersonProjection(projecting: personObject)

A property wrapper type that may be passed between threads.

A @ThreadSafe property contains a thread-safe reference to the underlying wrapped value. This reference is resolved to the thread on which the wrapped value is accessed. A new thread safe reference is created each time the property is accessed.