RealmKeyedCollection

public protocol RealmKeyedCollection : ThreadConfined, CustomStringConvertible, Sequence

A homogenous key-value collection of Objects which can be retrieved, filtered, sorted, and operated upon.

Properties

  • The Realm which manages the map, or nil if the map is unmanaged.

    Declaration

    Swift

    var realm: Realm? { get }
  • Indicates if the map can no longer be accessed.

    Declaration

    Swift

    var isInvalidated: Bool { get }
  • Returns the number of key-value pairs in this map.

    Declaration

    Swift

    var count: Int { get }
  • A human-readable description of the objects contained in the Map.

    Declaration

    Swift

    var description: String { get }

Mutation

  • Updates the value stored in the dictionary for the given key, or adds a new key-value pair if the key does not exist.

    Note

    Note:If the value being added to the dictionary is an unmanaged object and the dictionary is managed then that unmanaged object will be added to the Realm.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    func updateValue(_ value: Value, forKey key: Key)

    Parameters

    value

    a value’s key path predicate.

    forKey

    The direction to sort in.

  • Removes the given key and its associated object, only if the key exists in the dictionary. If the key does not exist, the dictionary will not be modified.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    func removeObject(for key: Key)
  • Removes all objects from the dictionary. The objects are not removed from the Realm that manages them.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    func removeAll()
  • Returns the value for a given key, or sets a value for a key should the subscript be used for an assign.

    Note

    Note:If the value being added to the dictionary is an unmanaged object and the dictionary is managed then that unmanaged object will be added to the Realm.

    Note

    Note:If the value being assigned for a key is nil then that key will be removed from the dictionary.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    subscript(key: Key) -> Value? { get set }

    Parameters

    key

    The key.

KVC

  • Returns a type of Value for a specified key if it exists in the map.

    Note that when using key-value coding, the key must be a string.

    Declaration

    Swift

    func value(forKey key: String) -> AnyObject?

    Parameters

    key

    The key to the property whose values are desired.

  • Returns a type of Value for a specified key if it exists in the map.

    Declaration

    Swift

    func value(forKeyPath keyPath: String) -> AnyObject?

    Parameters

    keyPath

    The key to the property whose values are desired.

  • Adds a given key-value pair to the dictionary or updates a given key should it already exist.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Swift

    func setValue(_ value: Any?, forKey key: String)

    Parameters

    value

    The object value.

    key

    The name of the property whose value should be set on each object.

Filtering

  • Returns a Results containing all matching values in the dictionary with the given predicate.

    Note

    This will return the values in the dictionary, and not the key-value pairs.

    Declaration

    Swift

    func filter(_ predicate: NSPredicate) -> Results<Value>

    Parameters

    predicate

    The predicate with which to filter the values.

  • Returns a Boolean value indicating whether the Map contains the key-value pair satisfies the given predicate

    Declaration

    Swift

    func contains(where predicate: @escaping (_ key: Key, _ value: Value) -> Bool) -> Bool

    Parameters

    where

    a closure that test if any key-pair of the given map represents the match.

Sorting

  • Returns a Results containing the objects in the dictionary, but sorted.

    Objects are sorted based on their values. For example, to sort a dictionary of Dates from neweset to oldest based, you might call dates.sorted(ascending: true).

    Declaration

    Swift

    func sorted(ascending: Bool) -> Results<Value>

    Parameters

    ascending

    The direction to sort in.

  • Returns a Results containing the objects in the dictionary, but sorted.

    Objects are sorted based on the values of the given key path. For example, to sort a dictionary of Students from youngest to oldest based on their age property, you might call students.sorted(byKeyPath: "age", ascending: true).

    Warning

    Dictionaries may only be sorted by properties of boolean, Date, NSDate, single and double-precision floating point, integer, and string types.

    Declaration

    Swift

    func sorted(byKeyPath keyPath: String, ascending: Bool) -> Results<Value>

    Parameters

    keyPath

    The key path to sort by.

    ascending

    The direction to sort in.

  • Returns a Results containing the objects in the dictionary, but sorted.

    Warning

    Dictionaries may only be sorted by properties of boolean, Date, NSDate, single and double-precision floating point, integer, and string types.

    Declaration

    Swift

    func sorted<S: Sequence>(by sortDescriptors: S) -> Results<Value>
        where S.Iterator.Element == SortDescriptor
  • Returns all of the keys in this dictionary.

    Declaration

    Swift

    var keys: [Key] { get }
  • Returns all of the values in the dictionary.

    Declaration

    Swift

    var values: [Value] { get }

Aggregate Operations

  • Returns the minimum (lowest) value of the given property among all the objects in the collection, or nil if the dictionary is empty.

    Warning

    Only a property whose type conforms to the MinMaxType protocol can be specified.

    Declaration

    Swift

    func min<T>(ofProperty property: String) -> T? where T : _HasPersistedType, T.PersistedType : MinMaxType

    Parameters

    property

    The name of a property whose minimum value is desired.

  • Returns the maximum (highest) value of the given property among all the objects in the dictionary, or nil if the dictionary is empty.

    Warning

    Only a property whose type conforms to the MinMaxType protocol can be specified.

    Declaration

    Swift

    func max<T>(ofProperty property: String) -> T? where T : _HasPersistedType, T.PersistedType : MinMaxType

    Parameters

    property

    The name of a property whose minimum value is desired.

  • Returns the sum of the given property for objects in the dictionary, or nil if the dictionary is empty.

    Warning

    Only names of properties of a type conforming to the AddableType protocol can be used.

    Declaration

    Swift

    func sum<T>(ofProperty property: String) -> T where T : _HasPersistedType, T.PersistedType : AddableType

    Parameters

    property

    The name of a property conforming to AddableType to calculate sum on.

  • Returns the average value of a given property over all the objects in the dictionary, or nil if the dictionary is empty.

    Warning

    Only a property whose type conforms to the AddableType protocol can be specified.

    Declaration

    Swift

    func average<T>(ofProperty property: String) -> T? where T : _HasPersistedType, T.PersistedType : AddableType

    Parameters

    property

    The name of a property whose values should be summed.

Notifications

  • Registers a block to be called each time the dictionary changes.

    The block will be asynchronously called with the initial dictionary, and then called again after each write transaction which changes either any of the keys or values in the dictionary.

    The change parameter that is passed to the block reports, in the form of keys within the dictionary, which of the key-value pairs were added, removed, or modified during each write transaction.

    At the time when the block is called, the dictionary will be fully evaluated and up-to-date, and as long as you do not perform a write transaction on the same thread or explicitly call realm.refresh(), accessing it will never perform blocking work.

    If no queue is given, notifications are delivered via the standard run loop, and so can’t be delivered while the run loop is blocked by other activity. If a queue is given, notifications are delivered to that queue instead. When notifications can’t be delivered instantly, multiple notifications may be coalesced into a single notification. This can include the notification with the initial collection.

    For example, the following code performs a write transaction immediately after adding the notification block, so there is no opportunity for the initial notification to be delivered first. As a result, the initial notification will reflect the state of the Realm after the write transaction.

    let myStringMap = myObject.stringMap
    print("myStringMap.count: \(myStringMap?.count)") // => 0
    let token = myStringMap.observe { changes in
        switch changes {
        case .initial(let myStringMap):
            // Will print "myStringMap.count: 1"
            print("myStringMap.count: \(myStringMap.count)")
           print("Dog Name: \(myStringMap["nameOfDog"])") // => "Rex"
            break
        case .update:
            // Will not be hit in this example
            break
        case .error:
            break
        }
    }
    try! realm.write {
        myStringMap["nameOfDog"] = "Rex"
    }
    // end of run loop execution context
    

    You must retain the returned token for as long as you want updates to be sent to the block. To stop receiving updates, call invalidate() on the token.

    Warning

    This method cannot be called during a write transaction, or when the containing Realm is read-only.

    Declaration

    Swift

    func observe(on queue: DispatchQueue?,
                 _ block: @escaping (RealmMapChange<Self>) -> Void)
    -> NotificationToken

    Parameters

    queue

    The serial dispatch queue to receive notification on. If nil, notifications are delivered to the current thread.

    block

    The block to be called whenever a change occurs.

    Return Value

    A token which must be held for as long as you want updates to be delivered.

  • Registers a block to be called each time the dictionary changes.

    The block will be asynchronously called with the initial dictionary, and then called again after each write transaction which changes either any of the keys or values in the dictionary.

    The change parameter that is passed to the block reports, in the form of keys within the dictionary, which of the key-value pairs were added, removed, or modified during each write transaction.

    At the time when the block is called, the dictionary will be fully evaluated and up-to-date, and as long as you do not perform a write transaction on the same thread or explicitly call realm.refresh(), accessing it will never perform blocking work.

    If no queue is given, notifications are delivered via the standard run loop, and so can’t be delivered while the run loop is blocked by other activity. If a queue is given, notifications are delivered to that queue instead. When notifications can’t be delivered instantly, multiple notifications may be coalesced into a single notification. This can include the notification with the initial collection.

    For example, the following code performs a write transaction immediately after adding the notification block, so there is no opportunity for the initial notification to be delivered first. As a result, the initial notification will reflect the state of the Realm after the write transaction.

    let myStringMap = myObject.stringMap
    print("myStringMap.count: \(myStringMap?.count)") // => 0
    let token = myStringMap.observe { changes in
        switch changes {
        case .initial(let myStringMap):
            // Will print "myStringMap.count: 1"
            print("myStringMap.count: \(myStringMap.count)")
           print("Dog Name: \(myStringMap["nameOfDog"])") // => "Rex"
            break
        case .update:
            // Will not be hit in this example
            break
        case .error:
            break
        }
    }
    try! realm.write {
        myStringMap["nameOfDog"] = "Rex"
    }
    // end of run loop execution context
    

    If no key paths are given, the block will be executed on any insertion, modification, or deletion for all object properties and the properties of any nested, linked objects. If a key path or key paths are provided, then the block will be called for changes which occur only on the provided key paths. For example, if:

    class Dog: Object {
        @Persisted var name: String
        @Persisted var age: Int
        @Persisted var toys: List<Toy>
    }
    // ...
    let dogs = myObject.mapOfDogs
    let token = dogs.observe(keyPaths: ["name"]) { changes in
        switch changes {
        case .initial(let dogs):
           // ...
        case .update:
           // This case is hit:
           // - after the token is initialized
           // - when the name property of an object in the
           // collection is modified
           // - when an element is inserted or removed
           //   from the collection.
           // This block is not triggered:
           // - when a value other than name is modified on
           //   one of the elements.
        case .error:
            // ...
        }
    }
    // end of run loop execution context
    
    • If the observed key path were ["toys.brand"], then any insertion or deletion to the toys list on any of the collection’s elements would trigger the block. Changes to the brand value on any Toy that is linked to a Dog in this collection will trigger the block. Changes to a value other than brand on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would also trigger a notification.
    • If the above example observed the ["toys"] key path, then any insertion, deletion, or modification to the toys list for any element in the collection would trigger the block. Changes to any value on any Toy that is linked to a Dog in this collection would not trigger the block. Any insertion or removal to the Dog type collection being observed would still trigger a notification.

    Note

    Multiple notification tokens on the same object which filter for separate key paths do not filter exclusively. If one key path change is satisfied for one notification token, then all notification token blocks for that object will execute.

    You must retain the returned token for as long as you want updates to be sent to the block. To stop receiving updates, call invalidate() on the token.

    Warning

    This method cannot be called during a write transaction, or when the containing Realm is read-only.

    Note

    The keyPaths parameter refers to object properties of the collection type and does not refer to particular key/value pairs within the collection.

    Declaration

    Swift

    func observe(keyPaths: [String]?,
                 on queue: DispatchQueue?,
                 _ block: @escaping (RealmMapChange<Self>) -> Void) -> NotificationToken

    Parameters

    keyPaths

    Only properties contained in the key paths array will trigger the block when they are modified. If nil, notifications will be delivered for any property change on the object. String key paths which do not correspond to a valid a property will throw an exception. See description above for more detail on linked properties.

    queue

    The serial dispatch queue to receive notification on. If nil, notifications are delivered to the current thread.

    block

    The block to be called whenever a change occurs.

    Return Value

    A token which must be held for as long as you want updates to be delivered.

Frozen Objects

  • Returns if this collection is frozen

    Declaration

    Swift

    var isFrozen: Bool { get }
  • Returns a frozen (immutable) snapshot of this collection.

    The frozen copy is an immutable collection which contains the same data as this collection currently contains, but will not update when writes are made to the containing Realm. Unlike live collections, frozen collections can be accessed from any thread.

    Warning

    This method cannot be called during a write transaction, or when the containing Realm is read-only.

    Warning

    Holding onto a frozen collection for an extended period while performing write transaction on the Realm may result in the Realm file growing to large sizes. See Realm.Configuration.maximumNumberOfActiveVersions for more information.

    Declaration

    Swift

    func freeze() -> Self
  • Returns a live (mutable) version of this frozen collection.

    This method resolves a reference to a live copy of the same frozen collection. If called on a live collection, will return itself.

    Declaration

    Swift

    func thaw() -> Self?

Available where Self: RealmSubscribable

Available where Value: OptionalProtocol, Value.Wrapped: ObjectBase

  • min(of:) Extension method

    Returns the minimum (lowest) value of the given property among all the objects in the collection, or nil if the collection is empty.

    Warning

    Only a property whose type conforms to the MinMaxType protocol can be specified.

    Declaration

    Swift

    func min<T>(of keyPath: KeyPath<Value.Wrapped, T>) -> T? where T : _HasPersistedType, T.PersistedType : MinMaxType

    Parameters

    keyPath

    The keyPath of a property whose minimum value is desired.

  • max(of:) Extension method

    Returns the maximum (highest) value of the given property among all the objects in the collection, or nil if the collection is empty.

    Warning

    Only a property whose type conforms to the MinMaxType protocol can be specified.

    Declaration

    Swift

    func max<T>(of keyPath: KeyPath<Value.Wrapped, T>) -> T? where T : _HasPersistedType, T.PersistedType : MinMaxType

    Parameters

    keyPath

    The keyPath of a property whose minimum value is desired.

  • sum(of:) Extension method

    Returns the sum of the given property for objects in the collection, or nil if the collection is empty.

    Warning

    Only names of properties of a type conforming to the AddableType protocol can be used.

    Declaration

    Swift

    func sum<T>(of keyPath: KeyPath<Value.Wrapped, T>) -> T where T : _HasPersistedType, T.PersistedType : AddableType

    Parameters

    keyPath

    The keyPath of a property conforming to AddableType to calculate sum on.

  • average(of:) Extension method

    Returns the average value of a given property over all the objects in the collection, or nil if the collection is empty.

    Warning

    Only a property whose type conforms to the AddableType protocol can be specified.

    Declaration

    Swift

    func average<T>(of keyPath: KeyPath<Value.Wrapped, T>) -> T? where T : _HasPersistedType, T.PersistedType : AddableType

    Parameters

    keyPath

    The keyPath of a property whose values should be summed.

Available where Value: OptionalProtocol, Value.Wrapped: ObjectBase, Value.Wrapped: RealmCollectionValue

  • sorted(by:ascending:) Extension method

    Returns a Results containing the objects in the collection, but sorted.

    Objects are sorted based on the values of the given key path. For example, to sort a collection of Students from youngest to oldest based on their age property, you might call students.sorted(byKeyPath: "age", ascending: true).

    Warning

    Collections may only be sorted by properties of boolean, Date, NSDate, single and double-precision floating point, integer, and string types.

    Declaration

    Swift

    func sorted<T>(by keyPath: KeyPath<Value.Wrapped, T>, ascending: Bool) -> Results<Value> where T : _HasPersistedType, T.PersistedType : SortableType

    Parameters

    keyPath

    The key path to sort by.

    ascending

    The direction to sort in.

Available where Value.PersistedType: MinMaxType

  • min() Extension method

    Returns the minimum (lowest) value of the collection, or nil if the collection is empty.

    Declaration

    Swift

    func min() -> Value?
  • max() Extension method

    Returns the maximum (highest) value of the collection, or nil if the collection is empty.

    Declaration

    Swift

    func max() -> Value?

Available where Value.PersistedType: AddableType

  • sum() Extension method

    Returns the sum of the values in the collection, or nil if the collection is empty.

    Declaration

    Swift

    func sum() -> Value
  • average() Extension method

    Returns the average of all of the values in the collection.

    Declaration

    Swift

    func average<T>() -> T? where T : _HasPersistedType, T.PersistedType : AddableType

Available where Value.PersistedType: SortableType

  • sorted(ascending:) Default implementation

    Default Implementation

    Returns a Results containing the objects in the collection, but sorted.

    Objects are sorted based on their values. For example, to sort a collection of Dates from neweset to oldest based, you might call dates.sorted(ascending: true).

    Declaration

    Swift

    func sorted(ascending: Bool = true) -> Results<Value>

    Parameters

    ascending

    The direction to sort in.