MutableSet

public final class MutableSet<Element> : RLMSwiftCollectionBase where Element : RealmCollectionValue
extension MutableSet: ObservableObject, RealmSubscribable
extension MutableSet: RealmCollection
extension MutableSet: Decodable where Element: Decodable
extension MutableSet: Encodable where Element: Encodable

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.

Properties

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

    Declaration

    Swift

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

    Declaration

    Swift

    public var isInvalidated: Bool { get }

Initializers

  • Creates a MutableSet that holds Realm model objects of type Element.

    Declaration

    Swift

    public override init()

Count

  • Returns the number of objects in this MutableSet.

    Declaration

    Swift

    public var count: Int { get }

KVC

  • Returns an Array containing the results of invoking valueForKey(_:) using key on each of the collection’s objects.

    Declaration

    Swift

    @nonobjc
    public func value(forKey key: String) -> [AnyObject]
  • Returns an Array containing the results of invoking valueForKeyPath(_:) using keyPath on each of the collection’s objects.

    Declaration

    Swift

    @nonobjc
    public func value(forKeyPath keyPath: String) -> [AnyObject]

    Parameters

    keyPath

    The key path to the property whose values are desired.

  • Invokes setValue(_:forKey:) on each of the collection’s objects using the specified value and key.

    Warning

    This method can only be called during a write transaction.

    Declaration

    Swift

    public override 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 objects matching the given predicate in the set.

    Declaration

    Swift

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

    Parameters

    predicate

    The predicate with which to filter the objects.

  • Returns a Boolean value indicating whether the Set contains the given object.

    Declaration

    Swift

    public func contains(_ object: Element) -> Bool

    Parameters

    object

    The element to find in the MutableSet.

  • Returns a Boolean value that indicates whether this set is a subset of the given set.

    Declaration

    Swift

    public func isSubset(of possibleSuperset: MutableSet<Element>) -> Bool

    Parameters

    object

    Another MutableSet to compare.

  • Returns a Boolean value that indicates whether this set intersects with another given set.

    Declaration

    Swift

    public func intersects(_ otherSet: MutableSet<Element>) -> Bool

    Parameters

    object

    Another MutableSet to compare.

Sorting

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

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

    Warning

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

    Declaration

    Swift

    public func sorted(byKeyPath keyPath: String, ascending: Bool = true) -> Results<Element>

    Parameters

    keyPath

    The key path to sort by.

    ascending

    The direction to sort in.

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

    Warning

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

    Declaration

    Swift

    public func sorted<S: Sequence>(by sortDescriptors: S) -> Results<Element>
        where S.Iterator.Element == SortDescriptor

Aggregate Operations

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

    Warning

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

    Declaration

    Swift

    public func min<T>(ofProperty property: String) -> T? where T : 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 set, or nil if the set is empty.

    Warning

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

    Declaration

    Swift

    public func max<T>(ofProperty property: String) -> T? where T : MinMaxType

    Parameters

    property

    The name of a property whose maximum value is desired.

  • Returns the sum of the values of a given property over all the objects in the set.

    Warning

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

    Declaration

    Swift

    public func sum<T>(ofProperty property: String) -> T where T : AddableType

    Parameters

    property

    The name of a property whose values should be summed.

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

    Warning

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

    Declaration

    Swift

    public func average<T>(ofProperty property: String) -> T? where T : AddableType

    Parameters

    property

    The name of a property whose average value should be calculated.

Mutation

  • Inserts an object to the set if not already present.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    public func insert(_ object: Element)

    Parameters

    object

    An object.

  • Inserts the given sequence of objects into the set if not already present.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    public func insert<S>(objectsIn objects: S) where Element == S.Element, S : Sequence
  • Removes an object in the set if present. The object is not removed from the Realm that manages it.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    public func remove(_ object: Element)

    Parameters

    object

    The object to remove.

  • Removes all objects from the set. The objects are not removed from the Realm that manages them.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    public func removeAll()
  • Mutates the set in place with the elements that are common to both this set and the given sequence.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    public func formIntersection(_ other: MutableSet<Element>)

    Parameters

    other

    Another set.

  • Mutates the set in place and removes the elements of the given set from this set.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    public func subtract(_ other: MutableSet<Element>)

    Parameters

    other

    Another set.

  • Inserts the elements of the given sequence into the set.

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    public func formUnion(_ other: MutableSet<Element>)

    Parameters

    other

    Another set.

Notifications

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

    The block will be asynchronously called with the initial results, and then called again after each write transaction which changes either any of the objects in the collection, or which objects are in the collection.

    The change parameter that is passed to the block reports, in the form of indices within the collection, which of the objects were added, removed, or modified during each write transaction. See the RealmCollectionChange documentation for more information on the change information supplied and an example of how to use it to update a UITableView.

    At the time when the block is called, the collection 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 results = realm.objects(Dog.self)
    print("dogs.count: \(dogs?.count)") // => 0
    let token = dogs.observe { changes in
        switch changes {
        case .initial(let dogs):
            // Will print "dogs.count: 1"
            print("dogs.count: \(dogs.count)")
            break
        case .update:
            // Will not be hit in this example
            break
        case .error:
            break
        }
    }
    try! realm.write {
        let dog = Dog()
        dog.name = "Rex"
        person.dogs.insert(dog)
    }
    // 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

    public func observe(on queue: DispatchQueue? = nil,
                        _ block: @escaping (RealmCollectionChange<MutableSet>) -> 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.

Frozen Objects

MutableSet

  • A publisher that emits Void each time the collection changes.

    Despite the name, this actually emits after the collection has changed.

    Declaration

    Swift

    public var objectWillChange: RealmPublishers.WillChange<MutableSet> { get }
  • The type of the objects stored within the set.

    Declaration

    Swift

    public typealias ElementType = Element

Sequence Support

  • Returns a RLMIterator that yields successive elements in the MutableSet.

    Declaration

    Swift

    public func makeIterator() -> RLMIterator<Element>
  • The position of the first element in a non-empty collection. Identical to endIndex in an empty collection.

    Declaration

    Swift

    public var startIndex: Int { get }
  • The collection’s “past the end” position. endIndex is not a valid argument to subscript, and is always reachable from startIndex by zero or more applications of successor().

    Declaration

    Swift

    public var endIndex: Int { get }
  • Declaration

    Swift

    public func index(after i: Int) -> Int
  • Declaration

    Swift

    public func index(before i: Int) -> Int

Object Retrieval

  • Warning

    Ordering is not guaranteed on a MutableSet. Subscripting is implemented for convenience should not be relied on.

    Declaration

    Swift

    public subscript(position: Int) -> Element { get }
  • Warning

    Ordering is not guaranteed on a MutableSet. first is implemented for convenience should not be relied on.

    Declaration

    Swift

    public var first: Element? { get }

Available where Element: MinMaxType

  • Returns the minimum (lowest) value in the set, or nil if the set is empty.

    Declaration

    Swift

    public func min() -> Element?
  • Returns the maximum (highest) value in the set, or nil if the set is empty.

    Declaration

    Swift

    public func max() -> Element?

Available where Element: AddableType

  • Returns the sum of the values in the set.

    Declaration

    Swift

    public func sum() -> Element
  • Returns the average of the values in the set, or nil if the set is empty.

    Declaration

    Swift

    public func average<T>() -> T? where T : AddableType

Available where Element: Decodable

Available where Element: Encodable