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 init(inMemoryIdentifier:)).

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

If you specifically want to ensure a Realm object 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.

Properties

  • Path to the file where this Realm is persisted.

    Declaration

    Swift

    public var path: String { return rlmRealm.path }
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  • Indicates if this Realm was opened in read-only mode.

    Declaration

    Swift

    public var readOnly: Bool { return rlmRealm.readOnly }
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  • The Schema used by this realm.

    Declaration

    Swift

    public var schema: Schema { return Schema(rlmRealm.schema) }
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  • The location of the default Realm as a string. Can be overridden.

    ~/Application Support/{bundle ID}/default.realm on OS X.

    default.realm in your application’s documents directory on iOS.

    Declaration

    Swift

    public class var defaultPath: String

    Return Value

    Location of the default Realm.

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Initializers

  • Obtains a Realm instance persisted at the specified file path. Defaults to Realm.defaultPath

    Declaration

    Swift

    public convenience init(path: String = Realm.defaultPath)

    Parameters

    path

    Path to the realm file.
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  • Obtains a Realm instance with persistence to a specific file path with options.

    Like init(path:), but with the ability to open read-only realms and get errors as an NSError inout parameter rather than exceptions.

    Declaration

    Swift

    public convenience init?(path: String, readOnly: Bool, encryptionKey: NSData? = nil, error: NSErrorPointer = nil)

    Parameters

    path

    Path to the file you want the data saved in.
    readOnly

    Bool indicating if this Realm is read-only (must use for read-only files).
    encryptionKey

    64-byte key to use to encrypt the data.
    error

    If an error occurs, upon return contains an NSError object that describes the problem. If you are not interested in possible errors, omit the argument, or pass in nil.
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  • Obtains a Realm instance for an un-persisted in-memory Realm. The identifier used to create this instance can be used to access the same in-memory Realm from multiple threads.

    Because in-memory Realms are not persisted, you must be sure to hold on to a reference to the Realm object returned from this for as long as you want the data to last. Realm’s internal cache of Realms will not keep the in-memory Realm alive across cycles of the run loop, so without a strong reference to the Realm a new Realm will be created each time. Note that Objects, Lists, and Results that refer to objects persisted in a Realm have a strong reference to the relevant Realm, as do NotifcationTokens.

    Declaration

    Swift

    public convenience init(inMemoryIdentifier: String)

    Parameters

    identifier

    A string used to identify a particular in-memory Realm.
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Transactions

  • Helper to perform actions contained within the given block inside a write transation.

    Declaration

    Swift

    public func write(block: (() -> Void))

    Parameters

    block

    The block to be executed inside a write transaction.
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  • Begins a write transaction in a Realm.

    Only one write transaction can be open at a time. Write transactions cannot be nested, and trying to begin a write transaction on a Realm which is already in a write transaction with throw an exception. Calls to beginWrite from Realm instances in other threads will block until the current write transaction completes.

    Before beginning the write transaction, beginWrite updates the Realm to the latest Realm version, as if refresh() was 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 in the write transaction is kept alive until the write transaction is committed.

    Declaration

    Swift

    public func beginWrite()
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  • Commits all writes operations in the current write transaction.

    After this is called, the Realm reverts back to being read-only.

    Calling this when not in a write transaction will throw an exception.

    Declaration

    Swift

    public func commitWrite()
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  • Revert all writes made in the current write transaction and end 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 reinstate deleted accessor objects. Any Objects which were added to the Realm will be invalidated rather than switching back to standalone objects. Given the following code:

    let oldObject = objects(ObjectType).first!
let newObject = ObjectType()

realm.beginWrite()
realm.add(newObject)
realm.delete(oldObject)
realm.cancelWrite()

    Both oldObject and newObject will return true for invalidated, but re-running the query which provided oldObject will once again return the valid object.

    Calling this when not in a write transaction will throw an exception.

    Declaration

    Swift

    public func cancelWrite()
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Adding and Creating objects

  • Adds or updates an object to be persisted it in this Realm.

    When ‘update’ is ‘true’, the object must have a primary key. If no objects exist in the Realm instance with the same primary key value, the object is inserted. Otherwise, the existing object is updated with any changed values.

    When added, all linked (child) objects referenced by this object will also be added to the Realm if they are not already in it. If the object or any linked objects already belong to a different Realm an exception will be thrown. Use one of the create functions to insert a copy of a persisted object into a different Realm.

    The object to be added must be valid and cannot have been previously deleted from a Realm (i.e. invalidated must be false).

    Declaration

    Swift

    public func add(object: Object, update: Bool = false)

    Parameters

    object

    Object to be added to this Realm.
    update

    If true will try to update existing objects with the same primary key.
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  • Adds or updates objects in the given sequence to be persisted it in this Realm.

    Declaration

    Swift

    public func add<S: SequenceType where S.Generator.Element: Object>(objects: S, update: Bool = false)

    Parameters

    objects

    A sequence which contains objects to be added to this Realm.
    update

    If true will try to update existing objects with the same primary key.
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  • Create an Object with the given object.

    Creates or updates an instance of this object and adds it to the Realm populating the object represented by value.

    When ‘update’ is ‘true’, the object must have a primary key. If no objects exist in the Realm instance with the same primary key value, the object is inserted. Otherwise, the existing object is updated with any changed values.

    Declaration

    Swift

    public func create<T: Object>(type: T.Type, value: AnyObject = [:], update: Bool = false) -> T

    Parameters

    type

    The object type to create.
    value

    The value used to populate the object. This can be any key/value coding compliant object, or a JSON dictionary such as those returned from the methods in NSJSONSerialization, or an Array with one object for each persisted property. An exception will be thrown if any required properties are not present and no default is set.

    When passing in an Array, all properties must be present, valid and in the same order as the properties defined in the model.
    update

    If true will try to update existing objects with the same primary key.

    Return Value

    The created object.

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Deleting objects

  • Deletes the given object from this Realm.

    Declaration

    Swift

    public func delete(object: Object)

    Parameters

    object

    The object to be deleted.
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  • Deletes the given objects from this Realm.

    Declaration

    Swift

    public func delete<S: SequenceType where S.Generator.Element: Object>(objects: S)

    Parameters

    object

    The objects to be deleted. This can be a List, Results, or any other enumerable SequenceType which generates Object.
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  • Deletes all objects from this Realm.

    Declaration

    Swift

    public func deleteAll()
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Object Retrieval

  • Returns all objects of the given type in the Realm.

    Declaration

    Swift

    public func objects<T: Object>(type: T.Type) -> Results<T>

    Parameters

    type

    The type of the objects to be returned.

    Return Value

    All objects of the given type in Realm.

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  • Get an object with the given primary key.

    Returns nil if no object exists with the given primary key.

    This method requires that primaryKey() be overridden on the given subclass.

    Declaration

    Swift

    public func objectForPrimaryKey<T: Object>(type: T.Type, key: AnyObject) -> T?

    Parameters

    type

    The type of the objects to be returned.
    key

    The primary key of the desired object.

    Return Value

    An object of type type or nil if an object with the given primary key does not exist.

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Notifications

  • Add a notification handler for changes in this Realm.

    Declaration

    Swift

    public func addNotificationBlock(block: 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 this notification occurred.

    Return Value

    A notification token which can later be passed to removeNotification(_:) to remove this notification.

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  • Remove a previously registered notification handler using the token returned from addNotificationBlock(_:)

    Declaration

    Swift

    public func removeNotification(notificationToken: NotificationToken)

    Parameters

    notificationToken

    The token returned from addNotificationBlock(_:) corresponding to the notification block to remove.
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Autorefresh and Refresh

  • Whether this Realm automatically updates 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 to false, you must manually call -refresh on the Realm to update it to get the latest version.

    Even with this 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 this is enabled.

    Disabling this on a Realm without any strong references to it will not have any effect, and it will switch back to YES the next time the Realm object is created. This is normally irrelevant as it means that there is nothing to refresh (as persisted Objects, Lists, and Results have strong references to the containing Realm), but it means that setting Realm().autorefresh = false in application(_:didFinishLaunchingWithOptions:) and only later storing Realm objects will not work.

    Defaults to true.

    Declaration

    Swift

    public var autorefresh: Bool
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  • Update a Realm and outstanding objects to point to the most recent data for this Realm.

    Declaration

    Swift

    public func refresh() -> Bool

    Return Value

    Whether the realm had any updates. Note that this may return true even if no data has actually changed.

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Invalidation

  • Invalidate all Objects and Results read from this 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 and List instances obtained from this Realm on the current thread are invalidated, and can not longer be used. 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 cannot be called on a read-only Realm.

    Declaration

    Swift

    public func invalidate()
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Writing a Copy

  • Write an encrypted and compacted copy of the Realm to the given path.

    The destination file cannot already exist.

    Note that if this is called from within a write transaction it writes the current data, and not data when the last write transaction was committed.

    Declaration

    Swift

    public func writeCopyToPath(path: String, encryptionKey: NSData? = nil) -> NSError?

    Parameters

    path

    Path to save the Realm to.
    encryptionKey

    Optional 64-byte encryption key to encrypt the new file with.

    Return Value

    If an error occurs, returns an NSError object, otherwise nil.

    Whether the realm was copied successfully.

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Encryption

  • Set the encryption key to use when opening Realms at a certain path.

    This can be used as an alternative to explicitly passing the key to Realm(path:, encryptionKey:, readOnly:, error:) each time a Realm instance is needed. The encryption key will be used any time a Realm is opened with Realm(path:) or Realm().

    If you do not want Realm to hold on to your encryption keys any longer than needed, then use Realm(path:, encryptionKey:, readOnly:, error:) rather than this method.

    Declaration

    Swift

    public class func setEncryptionKey(encryptionKey: NSData?, forPath: String = Realm.defaultPath)

    Parameters

    encryptionKey

    64-byte encryption key to use, or nil to unset.
    path

    Realm path to set the encryption key for.
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