Realm
public final class Realm
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.
Warning
Realm
instances are not thread safe and cannot be shared across threads or dispatch queues. You must
construct a new instance for each thread in which a Realm will be accessed. For dispatch queues, this means
that you must construct a new instance in each block which is dispatched, as a queue is not guaranteed to
run all of its blocks on the same thread.
-
The
Configuration
value that was used to create theRealm
instance.Declaration
Swift
public var configuration: Configuration
-
Indicates if the Realm contains any objects.
Declaration
Swift
public var isEmpty: Bool
-
Obtains an instance of the default Realm.
The default Realm is persisted as default.realm under the Documents directory of your Application on iOS, and in your application’s Application Support directory on OS X.
The default Realm is created using the default
Configuration
, which can be changed by setting theRealm.Configuration.defaultConfiguration
property to a new value.Throws
AnNSError
if the Realm could not be initialized.Declaration
Swift
public convenience init() throws
-
Obtains a
Realm
instance with the given configuration.Throws
An
NSError
if the Realm could not be initialized.Declaration
Swift
public convenience init(configuration: Configuration) throws
Parameters
configuration
A configuration value to use when creating the Realm.
-
Obtains a
Realm
instance persisted at a specified file URL.Throws
An
NSError
if the Realm could not be initialized.Declaration
Swift
public convenience init(fileURL: URL) throws
Parameters
fileURL
The local URL of the file the Realm should be saved at.
-
Asynchronously open a Realm and deliver it to a block on the given queue.
Opening a Realm asynchronously will perform all work needed to get the Realm to a usable state (such as running potentially time-consuming migrations) on a background thread before dispatching to the given queue. In addition, synchronized Realms wait for all remote content available at the time the operation began to be downloaded and available locally.
Note
The returned Realm is confined to the thread on which it was created. Because GCD does not guarantee that queues will always use the same thread, accessing the returned Realm outside the callback block (even if accessed from
callbackQueue
) is unsafe.Declaration
Swift
public static func asyncOpen(configuration: Realm.Configuration = .defaultConfiguration, callbackQueue: DispatchQueue = .main, callback: @escaping (Realm?, Realm.Error?) -> Void)
Parameters
configuration
A configuration object to use when opening the Realm.
callbackQueue
The dispatch queue on which the callback should be run.
callback
A callback block. If the Realm was successfully opened, an it will be passed in as an argument. Otherwise, a
Realm.Error
describing what went wrong will be passed to the block instead.
-
Performs actions contained within the given block inside a write transaction.
If the block throws an error, the transaction will be canceled and any changes made before the error will be rolled back.
Only one write transaction can be open at a time for each Realm file. Write transactions cannot be nested, and trying to begin a write transaction on a Realm which is already in a write transaction will throw an exception. Calls to
write
fromRealm
instances for the same Realm file in other threads or other processes will block until the current write transaction completes or is cancelled.Before beginning the write transaction,
write
updates theRealm
instance to the latest Realm version, as ifrefresh()
had been called, and generates notifications if applicable. This has no effect if the Realm was already up to date.Throws
An
NSError
if the transaction could not be completed successfully. Ifblock
throws, the function throws the propagatedErrorType
instead.Declaration
Swift
public func write(_ block: (() throws -> Void)) throws
Parameters
block
The block containing actions to perform.
-
Begins a write transaction on the Realm.
Only one write transaction can be open at a time for each Realm file. Write transactions cannot be nested, and trying to begin a write transaction on a Realm which is already in a write transaction will throw an exception. Calls to
beginWrite
fromRealm
instances for the same Realm file in other threads or other processes will block until the current write transaction completes or is cancelled.Before beginning the write transaction,
beginWrite
updates theRealm
instance to the latest Realm version, as ifrefresh()
had been called, and generates notifications if applicable. This has no effect if the Realm was already up to date.It is rarely a good idea to have write transactions span multiple cycles of the run loop, but if you do wish to do so you will need to ensure that the Realm participating in the write transaction is kept alive until the write transaction is committed.
Declaration
Swift
public func beginWrite()
-
Commits all write operations in the current write transaction, and ends the transaction.
After saving the changes and completing the write transaction, all notification blocks registered on this specific
Realm
instance are called synchronously. Notification blocks forRealm
instances on other threads and blocks registered for any Realm collection (including those on the current thread) are scheduled to be called synchronously.You can skip notifiying specific notification blocks about the changes made in this write transaction by passing in their associated notification tokens. This is primarily useful when the write transaction is saving changes already made in the UI and you do not want to have the notification block attempt to re-apply the same changes.
The tokens passed to this function must be for notifications for this Realm which were added on the same thread as the write transaction is being performed on. Notifications for different threads cannot be skipped using this method.
Warning
This method may only be called during a write transaction.
Throws
An
NSError
if the transaction could not be written due to running out of disk space or other i/o errors.Declaration
Swift
public func commitWrite(withoutNotifying tokens: [NotificationToken] = []) throws
-
Reverts all writes made in the current write transaction and ends the transaction.
This rolls back all objects in the Realm to the state they were in at the beginning of the write transaction, and then ends the transaction.
This restores the data for deleted objects, but does not revive invalidated object instances. Any
Object
s which were added to the Realm will be invalidated rather than becoming unmanaged.Given the following code:
let oldObject = objects(ObjectType).first! let newObject = ObjectType() realm.beginWrite() realm.add(newObject) realm.delete(oldObject) realm.cancelWrite()
Both
oldObject
andnewObject
will returntrue
forisInvalidated
, but re-running the query which providedoldObject
will once again return the valid object.KVO observers on any objects which were modified during the transaction will be notified about the change back to their initial values, but no other notifcations are produced by a cancelled write transaction.
Warning
This method may only be called during a write transaction.Declaration
Swift
public func cancelWrite()
-
Indicates whether the Realm is currently in a write transaction.
Warning
Do not simply check this property and then start a write transaction whenever an object needs to be created, updated, or removed. Doing so might cause a large number of write transactions to be created, degrading performance. Instead, always prefer performing multiple updates during a single transaction.Declaration
Swift
public var isInWriteTransaction: Bool
-
Adds or updates an existing object into the Realm.
Only pass
true
toupdate
if the object has a primary key. If no objects exist in the Realm with the same primary key value, the object is inserted. Otherwise, the existing object is updated with any changed values.When added, all child relationships referenced by this object will also be added to the Realm if they are not already in it. If the object or any related objects are already being managed by a different Realm an error will be thrown. Instead, use one of the
create
functions to insert a copy of a managed object into a different Realm.The object to be added must be valid and cannot have been previously deleted from a Realm (i.e.
isInvalidated
must befalse
).Declaration
Swift
public func add(_ object: Object, update: Bool = false)
Parameters
object
The object to be added to this Realm.
update
If
true
, the Realm will try to find an existing copy of the object (with the same primary key), and update it. Otherwise, the object will be added. -
Adds or updates all the objects in a collection into the Realm.
See
Warning
This method may only be called during a write transaction.
Declaration
Swift
public func add<S: Sequence>(_ objects: S, update: Bool = false) where S.Iterator.Element: Object
Parameters
objects
A sequence which contains objects to be added to the Realm.
update
If
true
, objects that are already in the Realm will be updated instead of added anew. -
Creates or updates a Realm object with a given value, adding it to the Realm and returning it.
Only pass
true
toupdate
if the object has a primary key. If no objects exist in the Realm with the same primary key value, the object is inserted. Otherwise, the existing object is updated with any changed values.The
value
argument can be a key-value coding compliant object, an array or dictionary returned from the methods inNSJSONSerialization
, or anArray
containing one element for each managed property. An exception will be thrown if any required properties are not present and those properties were not defined with default values. Do not pass in aLinkingObjects
instance, either by itself or as a member of a collection.When passing in an
Array
as thevalue
argument, all properties must be present, valid and in the same order as the properties defined in the model.Warning
This method may only be called during a write transaction.
Declaration
Swift
public func create<T: Object>(_ type: T.Type, value: Any = [:], update: Bool = false) -> T
Parameters
type
The type of the object to create.
value
The value used to populate the object.
update
If
true
, the Realm will try to find an existing copy of the object (with the same primary key), and update it. Otherwise, the object will be added.Return Value
The newly created object.
-
Deletes an object from the Realm. Once the object is deleted it is considered invalidated.
Warning
This method may only be called during a write transaction.
Declaration
Swift
public func delete(_ object: Object)
Parameters
object
The object to be deleted.
-
Deletes zero or more objects from the Realm.
Do not pass in a slice to a
Results
or any other auto-updating Realm collection type (for example, the type returned by the Swiftsuffix(_:)
standard library method). Instead, make a copy of the objects to delete usingArray()
, and pass that instead. Directly passing in a view into an auto-updating collection may result in ‘index out of bounds’ exceptions being thrown.Warning
This method may only be called during a write transaction.
Declaration
Swift
public func delete<S: Sequence>(_ objects: S) where S.Iterator.Element: Object
Parameters
objects
The objects to be deleted. This can be a
List<Object>
,Results<Object>
, or any other SwiftSequence
whose elements areObject
s (subject to the caveats above). -
Deletes all objects from the Realm.
Warning
This method may only be called during a write transaction.Declaration
Swift
public func deleteAll()
-
Returns all objects of the given type stored in the Realm.
Parameters
type
The type of the objects to be returned.
Return Value
A
Results
containing the objects. -
Retrieves the single instance of a given object type with the given primary key from the Realm.
This method requires that
primaryKey()
be overridden on the given object class.Declaration
Swift
public func object<T: Object, K>(ofType type: T.Type, forPrimaryKey key: K) -> T?
Parameters
type
The type of the object to be returned.
key
The primary key of the desired object.
Return Value
An object of type
type
, ornil
if no instance with the given primary key exists.
-
Adds a notification handler for changes made to this Realm, and returns a notification token.
Notification handlers are called after each write transaction is committed, independent of the thread or process.
Handler blocks are called on the same thread that they were added on, and may only be added on threads which are currently within a run loop. Unless you are specifically creating and running a run loop on a background thread, this will normally only be the main thread.
Notifications can’t be delivered as long as the run loop is blocked by other activity. When notifications can’t be delivered instantly, multiple notifications may be coalesced.
You must retain the returned token for as long as you want updates to be sent to the block. To stop receiving updates, call
stop()
on the token.Declaration
Swift
public func addNotificationBlock(_ block: @escaping NotificationBlock) -> NotificationToken
Parameters
block
A block which is called to process Realm notifications. It receives the following parameters:
notification
: the incoming notification;realm
: the Realm for which the notification occurred.Return Value
A token which must be held for as long as you wish to continue receiving change notifications.
-
Set this property to
true
to automatically update this Realm when changes happen in other threads.If set to
true
(the default), changes made on other threads will be reflected in this Realm on the next cycle of the run loop after the changes are committed. If set tofalse
, you must manually callrefresh()
on the Realm to update it to get the latest data.Note that by default, background threads do not have an active run loop and you will need to manually call
refresh()
in order to update to the latest version, even ifautorefresh
is set totrue
.Even with this property enabled, you can still call
refresh()
at any time to update the Realm before the automatic refresh would occur.Notifications are sent when a write transaction is committed whether or not automatic refreshing is enabled.
Disabling
autorefresh
on aRealm
without any strong references to it will not have any effect, andautorefresh
will revert back totrue
the next time the Realm is created. This is normally irrelevant as it means that there is nothing to refresh (as managedObject
s,List
s, andResults
have strong references to theRealm
that manages them), but it means that settingautorefresh = false
inapplication(_:didFinishLaunchingWithOptions:)
and only later storing Realm objects will not work.Defaults to
true
.Declaration
Swift
public var autorefresh: Bool
-
Updates the Realm and outstanding objects managed by the Realm to point to the most recent data.
Declaration
Swift
public func refresh() -> Bool
Return Value
Whether there were any updates for the Realm. Note that
true
may be returned even if no data actually changed.
-
Invalidates all
Object
s,Results
,LinkingObjects
, andList
s managed by the Realm.A Realm holds a read lock on the version of the data accessed by it, so that changes made to the Realm on different threads do not modify or delete the data seen by this Realm. Calling this method releases the read lock, allowing the space used on disk to be reused by later write transactions rather than growing the file. This method should be called before performing long blocking operations on a background thread on which you previously read data from the Realm which you no longer need.
All
Object
,Results
andList
instances obtained from thisRealm
instance on the current thread are invalidated.Object
s andArray
s cannot be used.Results
will become empty. The Realm itself remains valid, and a new read transaction is implicitly begun the next time data is read from the Realm.Calling this method multiple times in a row without reading any data from the Realm, or before ever reading any data from the Realm, is a no-op. This method may not be called on a read-only Realm.
Declaration
Swift
public func invalidate()
-
Writes a compacted and optionally encrypted copy of the Realm to the given local URL.
The destination file cannot already exist.
Note that if this method is called from within a write transaction, the current data is written, not the data from the point when the previous write transaction was committed.
Throws
An
NSError
if the copy could not be written.Declaration
Swift
public func writeCopy(toFile fileURL: URL, encryptionKey: Data? = nil) throws
Parameters
fileURL
Local URL to save the Realm to.
encryptionKey
Optional 64-byte encryption key to encrypt the new file with.
-
Struct that describes the error codes within the Realm error domain. The values can be used to catch a variety of recoverable errors, especially those happening when initializing a Realm instance.
See morelet realm: Realm? do { realm = try Realm() } catch Realm.Error.incompatibleLockFile { print("Realm Browser app may be attached to Realm on device?") }
Declaration
Swift
public struct Error
-
Performs the given Realm configuration’s migration block on a Realm at the given path.
This method is called automatically when opening a Realm for the first time and does not need to be called explicitly. You can choose to call this method to control exactly when and how migrations are performed.
Declaration
Swift
public static func performMigration(for configuration: Realm.Configuration = Realm.Configuration.defaultConfiguration) throws
Parameters
configuration
The Realm configuration used to open and migrate the Realm.
-
Returns whether two
Realm
isntances are equal.Declaration
Swift
public static func == (lhs: Realm, rhs: Realm) -> Bool
-
A notification indicating that changes were made to a Realm.
See moreDeclaration
Swift
public enum Notification: String
-
A
Configuration
instance describes the different options used to create an instance of a Realm.Configuration
instances are just plain Swift structs. UnlikeRealm
s andObject
s, they can be freely shared between threads as long as you do not mutate them.Creating configuration values for class subsets (by setting the
See moreobjectClasses
property) can be expensive. Because of this, you will normally want to cache and reuse a single configuration value for each distinct configuration rather than creating a new value each time you open a Realm.Declaration
Swift
public struct Configuration
-
A human-readable description of the configuration value.
Declaration
Swift
public var description: String
-
Returns the same object as the one referenced when the
ThreadSafeReference
was first created, but resolved for the current Realm for this thread. Returnsnil
if this object was deleted after the reference was created.Warning
A
ThreadSafeReference
object must be resolved at most once. Failing to resolve aThreadSafeReference
will result in the source version of the Realm being pinned until the reference is deallocated. An exception will be thrown if a reference is resolved more than once.Warning
Cannot call within a write transaction.
Note
Will refresh this Realm if the source Realm was at a later version than this one.
See
ThreadSafeReference(to:)
Declaration
Swift
public func resolve<Confined: ThreadConfined>(_ reference: ThreadSafeReference<Confined>) -> Confined?
Parameters
reference
The thread-safe reference to the thread-confined object to resolve in this Realm.