LinkingObjects

public final class LinkingObjects<T: Object>: LinkingObjectsBase

LinkingObjects is an auto-updating container type. It represents a collection of objects that link to its parent object.

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.

Properties

  • The element type contained in this collection.

    Declaration

    Swift

    public typealias Element = T
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  • Returns the object at the given index.

    Declaration

    Swift

    public subscript(index: Int) -> T

    Parameters

    index

    The index.

    Return Value

    The object at the given index.

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  • The Realm which manages this linking objects collection, or nil if the collection is unmanaged.

    Declaration

    Swift

    public var realm: Realm? { return rlmResults.attached ? Realm(rlmResults.realm) : nil }
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  • Indicates if the linking objects collection is no longer valid.

    The linking objects collection becomes invalid if invalidate is called on the containing realm.

    An invalidated linking objects can be accessed, but will always be empty.

    Declaration

    Swift

    public var invalidated: Bool { return rlmResults.invalidated }
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  • The number of objects in the linking objects.

    Declaration

    Swift

    public var count: Int { return Int(rlmResults.count) }
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Initializers

  • Creates an instance of a LinkingObjects. This initializer should only be called when declaring a property on a Realm model.

    Declaration

    Swift

    public init(fromType type: T.Type, property propertyName: String)

    Parameters

    type

    The type of the object owning the property this LinkingObjects should refer to.
    propertyName

    The property name of the property this LinkingObjects should refer to.
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  • Returns a description of the objects contained within the linking objects.

    Declaration

    Swift

    public override var description: String
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Index Retrieval

  • Returns the index of the given object, or nil if the object is not present.

    Declaration

    Swift

    public func indexOf(object: T) -> Int?

    Parameters

    object

    The object whose index is being queried.

    Return Value

    The index of the given object, or nil if the object is not present.

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  • Returns the index of the first object matching the given predicate, or nil if no objects match.

    Declaration

    Swift

    public func indexOf(predicate: NSPredicate) -> Int?

    Parameters

    predicate

    The predicate with which to filter the objects.

    Return Value

    The index of the first matching object, or nil if no objects match.

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  • Returns the index of the first object matching the given predicate, or nil if no objects match.

    Declaration

    Swift

    public func indexOf(predicateFormat: String, _ args: AnyObject...) -> Int?

    Parameters

    predicateFormat

    A predicate format string, optionally followed by a variable number of arguments.

    Return Value

    The index of the first matching object, or nil if no objects match.

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Object Retrieval

  • Returns the first object in the linking objects collection, or nil if the collection is empty.

    Declaration

    Swift

    public var first: T? { return unsafeBitCast(rlmResults.firstObject(), Optional<T>.self) }
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  • Returns the last object in the linking objects collection, or nil if collection is empty.

    Declaration

    Swift

    public var last: T? { return unsafeBitCast(rlmResults.lastObject(), Optional<T>.self) }
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KVC

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

    Declaration

    Swift

    public override func valueForKey(key: String) -> AnyObject?

    Parameters

    key

    The name of the property.

    Return Value

    An Array containing the results.

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  • Returns an Array containing the results of invoking valueForKeyPath(_:) with keyPath on each of the linking objects collection’s objects.

    Declaration

    Swift

    public override func valueForKeyPath(keyPath: String) -> AnyObject?

    Parameters

    keyPath

    The key path to the property.

    Return Value

    An Array containing the results.

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

    Warning

    This method may only be called during a write transaction.

    Declaration

    Swift

    public override func setValue(value: AnyObject?, forKey key: String)

    Parameters

    value

    The object value.
    key

    The name of the property.
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Filtering

  • Returns all the objects matching the given predicate in the linking objects collection.

    Declaration

    Swift

    public func filter(predicateFormat: String, _ args: AnyObject...) -> Results<T>

    Parameters

    predicateFormat

    A predicate format string, optionally followed by a variable number of arguments.

    Return Value

    A Results object containing the results.

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  • Returns all the objects matching the given predicate in the linking objects collection.

    Declaration

    Swift

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

    Parameters

    predicate

    The predicate with which to filter the objects.

    Return Value

    A Results object containing the results.

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Sorting

  • Returns a Results containing the linking objects collection’s elements sorted by the given property name.

    Declaration

    Swift

    public func sorted(property: String, ascending: Bool = true) -> Results<T>

    Parameters

    property

    The property name to sort by.
    ascending

    The direction to sort in.

    Return Value

    A Results object.

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  • Returns a Results containing the linking objects collection’s elements sorted by the given sort descriptors.

    Declaration

    Swift

    public func sorted<S: SequenceType where S.Generator.Element == SortDescriptor>(sortDescriptors: S) -> Results<T>

    Parameters

    sortDescriptors

    A sequence of SortDescriptors to sort by.

    Return Value

    A Results object.

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Aggregate Operations

  • Returns the minimum (lowest) value of the given property among all the objects represented by the linking objects collection.

    Warning

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

    Declaration

    Swift

    public func min<U: MinMaxType>(property: String) -> U?

    Parameters

    property

    The name of a property whose minimum value is desired.

    Return Value

    The minimum value of the property, or nil if the collection is empty.

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  • Returns the maximum (highest) value of the given property among all the objects represented by the linking objects collection.

    Warning

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

    Declaration

    Swift

    public func max<U: MinMaxType>(property: String) -> U?

    Parameters

    property

    The name of a property whose minimum value is desired.

    Return Value

    The maximum value of the property, or nil if the collection is empty.

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  • Returns the sum of the values of a given property over all the objects represented by the linking objects collection.

    Warning

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

    Declaration

    Swift

    public func sum<U: AddableType>(property: String) -> U

    Parameters

    property

    The name of a property whose values should be summed.

    Return Value

    The sum of the given property.

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  • Returns the average value of a given property over all the objects represented by the linking objects collection.

    Warning

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

    Declaration

    Swift

    public func average<U: AddableType>(property: String) -> U?

    Parameters

    property

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

    Return Value

    The average value of the given property, or nil if the collection is empty.

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Notifications

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

    The block will be asynchronously called with the initial linking objects collection, 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 linking objects 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.

    Notifications are delivered via the standard run loop, and so can’t be delivered while the run loop is blocked by other activity. When notifications can’t be delivered instantly, multiple notifications may be coalesced into a single notification. This can include the notification with the initial set of objects. 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 dog = realm.objects(Dog).first!
let owners = dog.owners
print("owners.count: \(owners.count)") // => 0
let token = owners.addNotificationBlock { (changes: RealmCollectionChange) in
    switch changes {
        case .Initial(let owners):
            // Will print "owners.count: 1"
            print("owners.count: \(owners.count)")
            break
        case .Update:
            // Will not be hit in this example
            break
        case .Error:
            break
    }
}
try! realm.write {
    realm.add(Person.self, value: ["name": "Mark", dogs: [dog]])
}
// end of runloop execution context

    You must retain the returned token for as long as you want updates to continue to be sent to the block. To stop receiving updates, call stop() 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 addNotificationBlock(block: (RealmCollectionChange<LinkingObjects> -> Void)) -> NotificationToken

    Parameters

    block

    The block to be called whenever a change occurs.

    Return Value

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

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Sequence Support

  • Returns a GeneratorOf<T> that yields successive elements in the results.

    Declaration

    Swift

    public func generate() -> RLMGenerator<T>
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Collection Support

  • The position of the first element in a non-empty collection. Identical to endIndex in an empty collection.

    Declaration

    Swift

    public var startIndex: Int { return 0 }
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  • 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 { return count }
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