LinkingObjects

public final class LinkingObjects<T: Object>: LinkingObjectsBase

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

LinkingObjects can be queried with the same predicates as List<T> and Results<T>.

LinkingObjects always reflect 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 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. The property must be declared as let and cannot be dynamic.

Properties

  • 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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  • Element type contained in this collection.

    Declaration

    Swift

    public typealias Element = T
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  • Returns the Realm these linking objects are associated with.

    Declaration

    Swift

    public var realm: Realm? { return rlmResults.attached ? Realm(rlmResults.realm) : nil }
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  • Indicates if the linking objects can no longer be accessed.

    Linking objects can no longer be accessed if invalidate is called on the containing Realm.

    Declaration

    Swift

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

    Declaration

    Swift

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

  • Creates 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 originating type linking to this object type.
    propertyName

    The property name of the incoming relationship this LinkingObjects should refer to.
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  • Returns a human-readable description of the objects contained in these 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 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

    The predicate format string which can accept variable 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 collection, or nil if empty.

    Declaration

    Swift

    public var first: T? { return unsafeBitCast(rlmResults.firstObject(), Optional<T>.self) }
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  • Returns the last object in the collection, or nil if 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(_:) using key on each of the collection’s objects.

    Declaration

    Swift

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

    Parameters

    key

    The name of the property.

    Return Value

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

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

    Declaration

    Swift

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

    Parameters

    keyPath

    The key path to the property.

    Return Value

    Array containing the results of invoking valueForKeyPath(_:) using keyPath on each of the collection’s objects.

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  • 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: AnyObject?, forKey key: String)

    Parameters

    value

    The object value.
    key

    The name of the property.
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Filtering

  • Filters the collection to the objects that match the given predicate.

    Declaration

    Swift

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

    Parameters

    predicateFormat

    The predicate format string which can accept variable arguments.

    Return Value

    Results containing objects that match the given predicate.

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  • Filters the collection to the objects that match the given predicate.

    Declaration

    Swift

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

    Parameters

    predicate

    The predicate to filter the objects.

    Return Value

    Results containing objects that match the given predicate.

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Sorting

  • Returns Results with 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 by.

    Return Value

    Results with elements sorted by the given property name.

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  • Returns Results with 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

    SortDescriptors to sort by.

    Return Value

    Results with elements sorted by the given sort descriptors.

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Aggregate Operations

  • Returns the minimum value of the given property.

    Warning

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

    Declaration

    Swift

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

    Parameters

    property

    The name of a property conforming to MinMaxType to look for a minimum on.

    Return Value

    The minimum value for the property amongst objects in the collection, or nil if the collection is empty.

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  • Returns the maximum value of the given property.

    Warning

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

    Declaration

    Swift

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

    Parameters

    property

    The name of a property conforming to MinMaxType to look for a maximum on.

    Return Value

    The maximum value for the property amongst objects in the collection, or nil if the collection is empty.

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  • Returns the sum of the given property for objects in the collection.

    Warning

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

    Declaration

    Swift

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

    Parameters

    property

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

    Return Value

    The sum of the given property over all objects in the collection.

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  • Returns the average of the given property for objects in the collection.

    Warning

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

    Declaration

    Swift

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

    Parameters

    property

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

    Return Value

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

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Notifications

  • Register a block to be called each time the LinkingObjects changes.

    The block will be asynchronously called with the initial set of objects, 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.

    This version of this method reports which of the objects in the collection were added, removed, or modified in each write transaction as indices within the collection. 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 LinkingObjects object 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 source realm is read-only.

    Declaration

    Swift

    public func addNotificationBlock(block: (RealmCollectionChange<LinkingObjects> -> Void)) -> NotificationToken

    Parameters

    block

    The block to be called with the evaluated linking objects and change information.

    Return Value

    A token which must be held 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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