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
.
-
Element type contained in this collection.
Declaration
Swift
public typealias Element = T
-
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
. -
Returns the Realm these linking objects are associated with.
Declaration
Swift
public var realm: Realm? { return rlmResults.attached ? Realm(rlmResults.realm) : nil }
-
Returns the number of objects in these linking objects.
Declaration
Swift
public var count: Int { return Int(rlmResults.count) }
-
Undocumented
Declaration
Swift
public final class LinkingObjects<T: Object>: LinkingObjectsBase
-
Returns a human-readable description of the objects contained in these linking objects.
Declaration
Swift
public override var description: String
-
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. -
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. -
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.
-
Returns the first object in the collection, or
nil
if empty.Declaration
Swift
public var first: T? { return unsafeBitCast(rlmResults.firstObject(), Optional<T>.self) }
-
Returns the last object in the collection, or
nil
if empty.Declaration
Swift
public var last: T? { return unsafeBitCast(rlmResults.lastObject(), Optional<T>.self) }
-
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. -
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. -
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.
-
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.
-
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.
-
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. -
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
SortDescriptor
s to sort by.Return Value
Results
with elements sorted by the given sort descriptors.
-
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. -
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. -
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.
-
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.
-
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.
If an error occurs the block will be called with
nil
for the linkingObjects parameter and a non-nil
error. Currently the only errors that can occur are when opening the Realm on the background worker thread fails.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 results. 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 { (owners, error) in // Only fired once for the example print(owners.count: \(owners.count)
) // will only printowners.count: 1
} try! realm.write { realm.add(Person.self, value: [name
:Mark
, dogs: [dog]]) } // end of runloop execution contextYou 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: (linkingObjects: LinkingObjects<T>?, error: NSError?) -> ()) -> NotificationToken
Parameters
block
The block to be called with the evaluated linking objects.
Return Value
A token which must be held for as long as you want query results to be delivered.
-
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 printowners.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 contextYou 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.
-
Returns a
GeneratorOf<T>
that yields successive elements in the results.Declaration
Swift
public func generate() -> RLMGenerator<T>
-
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 }
-
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 }