Classes

A Realm instance (also referred to as a Realm) represents a Realm database.

Realms can either be stored on disk (see init(path:)) or in memory (see Configuration).

Realm instances are cached internally, and constructing equivalent Realm objects (for example, by using the same path or identifier) produces limited overhead.

If you specifically want to ensure a Realm instance is destroyed (for example, if you wish to open a Realm, check some property, and then possibly delete the Realm file and re-open it), place the code which uses the Realm within an autoreleasepool {} and ensure you have no other strong references to it.

LinkingObjects is an auto-updating container type. It represents zero or more objects that are linked to its owning model object through a property relationship.

LinkingObjects can be queried with the same predicates as List<T> and Results<T>.

LinkingObjects always reflects the current state of the Realm on the current thread, including during write transactions on the current thread. The one exception to this is when using for...in enumeration, which will always enumerate over the linking objects that were present when the enumeration is begun, even if some of them are deleted or modified to no longer link to the target object during the enumeration.

LinkingObjects can only be used as a property on Object models. Properties of this type must be declared as let and cannot be dynamic.

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 of Object it stores.

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<T>.

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

Migration instances encapsulate information intended to facilitate a schema migration.

A Migration instance is passed into a user-defined MigrationBlock block when updating the version of a Realm. This instance provides access to the old and new database schemas, the objects in the Realm, and provides functionality for modifying the Realm during the migration.

Object is a class used to define Realm model objects.

In Realm you define your model classes by subclassing Object and adding properties to be managed. You then instantiate and use your custom subclasses instead of using the Object class directly.

class Dog: Object {
    dynamic var name: String = ""
    dynamic var adopted: Bool = false
    let siblings = List<Dog>()
}

Supported property types

• String, NSString
• Int
• Int8, Int16, Int32, Int64
• Float
• Double
• Bool
• Date, NSDate
• Data, NSData
• RealmOptional<T> for optional numeric properties
• Object subclasses, to model many-to-one relationships
• List<T>, to model many-to-many relationships

String, NSString, Date, NSDate, Data, NSData and Object subclass properties can be declared as optional. Int, Int8, Int16, Int32, Int64, Float, Double, Bool, and List properties cannot. To store an optional number, use RealmOptional<Int>, RealmOptional<Float>, RealmOptional<Double>, or RealmOptional<Bool> instead, which wraps an optional numeric value.

All property types except for List and RealmOptional must be declared as dynamic var. List and RealmOptional properties must be declared as non-dynamic let properties. Swift lazy properties are not allowed.

Note that none of the restrictions listed above apply to properties that are configured to be ignored by Realm.

Querying

You can retrieve all objects of a given type from a Realm by calling the objects(_:) instance method.

Relationships

See our Cocoa guide for more details.

This class represents Realm model object schemas.

When using Realm, ObjectSchema instances allow performing migrations and introspecting the database’s schema.

Object schemas map to tables in the core database.

A RealmOptional instance represents an optional value for types that can’t be directly declared as dynamic 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.

Property instances represent properties managed by a Realm in the context of an object schema. Such properties may be persisted to a Realm file or computed from other data in the Realm.

When using Realm, property instances allow performing migrations and introspecting the database’s schema.

Property instances map to columns in the core database.

An iterator for a RealmCollection instance.

A type-erased RealmCollection.

Instances of RealmCollection forward operations to an opaque underlying collection having the same Element type.

Results is an auto-updating container type in Realm returned from object queries.

Results can be queried with the same predicates as List<T>, and you can chain queries to further filter query results.

Results always reflect the current state of the Realm on the current thread, including during write transactions on the current thread. The one exception to this is when using for...in enumeration, which will always enumerate over the objects which matched the query when the enumeration is begun, even if some of them are deleted or modified to be excluded by the filter during the enumeration.

Results are lazily evaluated the first time they are accessed; they only run queries when the result of the query is requested. This means that chaining several temporary Results to sort and filter your data does not perform any unnecessary work processing the intermediate state.

Once the results have been evaluated or a notification block has been added, the results are eagerly kept up-to-date, with the work done to keep them up-to-date done on a background thread whenever possible.

Results instances cannot be directly instantiated.

Schema instances represent collections of model object schemas managed by a Realm.

When using Realm, Schema instances allow performing migrations and introspecting the database’s schema.

Schemas map to collections of tables in the core database.

This model is used for requesting changes to a Realm’s permissions.

It should be used in conjunction with an SyncUser’s management Realm.

See https://realm.io/docs/realm-object-server/#permissions for general documentation.