List
public final class List<Element> : ListBase where Element : RealmCollectionValue
extension List: ObservableObject, RealmSubscribable
extension List: RealmCollection
extension List: MutableCollection
extension List: Decodable where Element: Decodable
extension List: Encodable where Element: Encodable
List
is the container type in Realm used to define to-many relationships.
Like Swift’s Array
, List
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
,
and Date
(and their optional versions)
Unlike Swift’s native collections, List
s are reference types, and are only immutable if the Realm that manages them
is opened as read-only.
Lists can be filtered and sorted with the same predicates as Results<Element>
.
Properties of List
type defined on Object
subclasses must be declared as let
and cannot be dynamic
.
-
The Realm which manages the list, or
nil
if the list is unmanaged.Declaration
Swift
public var realm: Realm? { get }
-
Indicates if the list can no longer be accessed.
Declaration
Swift
public var isInvalidated: Bool { get }
-
Creates a
List
that holds Realm model objects of typeElement
.Declaration
Swift
public override init()
-
Returns the index of an object in the list, or
nil
if the object is not present.Declaration
Swift
public func index(of object: Element) -> Int?
Parameters
object
An object to find.
-
Returns the index of the first object in the list matching the predicate, or
nil
if no objects match.Declaration
Swift
public func index(matching predicate: NSPredicate) -> Int?
Parameters
predicate
The predicate with which to filter the objects.
-
Returns the object at the given index (get), or replaces the object at the given index (set).
Warning
You can only set an object during a write transaction.
Declaration
Swift
public subscript(position: Int) -> Element { get set }
Parameters
index
The index of the object to retrieve or replace.
-
Returns the first object in the list, or
nil
if the list is empty.Declaration
Swift
public var first: Element? { get }
-
Returns the last object in the list, or
nil
if the list is empty.Declaration
Swift
public var last: Element? { get }
-
Returns an
Array
containing the results of invokingvalueForKey(_:)
usingkey
on each of the collection’s objects.Declaration
Swift
@nonobjc public func value(forKey key: String) -> [AnyObject]
-
Returns an
Array
containing the results of invokingvalueForKeyPath(_:)
usingkeyPath
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 specifiedvalue
andkey
.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.
-
Returns a
Results
containing the objects in the list, but sorted.Objects are sorted based on the values of the given key path. For example, to sort a list of
Student
s from youngest to oldest based on theirage
property, you might callstudents.sorted(byKeyPath: "age", ascending: true)
.Warning
Lists 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 list, but sorted.Warning
Lists 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
-
Returns the minimum (lowest) value of the given property among all the objects in the list, or
nil
if the list 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 list, or
nil
if the list 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 list.
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 list, or
nil
if the list is empty.Warning
Only a property whose type conforms to the
AddableType
protocol can be specified.Declaration
Swift
public func average(ofProperty property: String) -> Double?
Parameters
property
The name of a property whose average value should be calculated.
-
Appends the given object to the end of the list.
If the object is managed by a different Realm than the receiver, a copy is made and added to the Realm managing the receiver.
Warning
This method may only be called during a write transaction.
Declaration
Swift
public func append(_ object: Element)
Parameters
object
An object.
-
Appends the objects in the given sequence to the end of the list.
Warning
This method may only be called during a write transaction.Declaration
Swift
public func append<S>(objectsIn objects: S) where Element == S.Element, S : Sequence
-
Inserts an object at the given index.
Warning
This method may only be called during a write transaction.
Warning
This method will throw an exception if called with an invalid index.
Declaration
Swift
public func insert(_ object: Element, at index: Int)
Parameters
object
An object.
index
The index at which to insert the object.
-
Removes an object at the given index. The object is not removed from the Realm that manages it.
Warning
This method may only be called during a write transaction.
Warning
This method will throw an exception if called with an invalid index.
Declaration
Swift
public func remove(at index: Int)
Parameters
index
The index at which to remove the object.
-
Removes all objects from the list. 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()
-
Replaces an object at the given index with a new object.
Warning
This method may only be called during a write transaction.
Warning
This method will throw an exception if called with an invalid index.
Declaration
Swift
public func replace(index: Int, object: Element)
Parameters
index
The index of the object to be replaced.
object
An object.
-
Moves the object at the given source index to the given destination index.
Warning
This method may only be called during a write transaction.
Warning
This method will throw an exception if called with invalid indices.
Declaration
Swift
public func move(from: Int, to: Int)
Parameters
from
The index of the object to be moved.
to
index to which the object at
from
should be moved. -
Exchanges the objects in the list at given indices.
Warning
This method may only be called during a write transaction.
Warning
This method will throw an exception if called with invalid indices.
Declaration
Swift
public func swapAt(_ index1: Int, _ index2: Int)
Parameters
index1
The index of the object which should replace the object at index
index2
.index2
The index of the object which should replace the object at index
index1
.
-
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 theRealmCollectionChange
documentation for more information on the change information supplied and an example of how to use it to update aUITableView
.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.append(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<List>) -> 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.
-
Declaration
Swift
public var isFrozen: Bool { get }
-
Declaration
Swift
public func freeze() -> List
-
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: Publishers.WillChange<List> { get }
-
The type of the objects stored within the list.
Declaration
Swift
public typealias ElementType = Element
-
Returns a
RLMIterator
that yields successive elements in theList
.Declaration
Swift
public func makeIterator() -> RLMIterator<Element>
-
Replace the given
subRange
of elements withnewElements
.Declaration
Swift
public func replaceSubrange<C: Collection, R>(_ subrange: R, with newElements: C) where C.Iterator.Element == Element, R: RangeExpression, List<Element>.Index == R.Bound
Parameters
subrange
The range of elements to be replaced.
newElements
The new elements to be inserted into the List.
-
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
-
Declaration
Swift
public typealias SubSequence = Slice<List>
-
Returns the objects at the given range (get), or replaces the objects at the given range with new objects (set).
Warning
Objects may only be set during a write transaction.
Declaration
Swift
public subscript(bounds: Range<Int>) -> SubSequence { get set }
Parameters
index
The index of the object to retrieve or replace.
-
Removes the specified number of objects from the beginning of the list. 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 removeFirst(_ number: Int = 1)
-
Removes the specified number of objects from the end of the list. 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 removeLast(_ number: Int = 1)
-
Inserts the items in the given collection into the list at the given position.
Warning
This method may only be called during a write transaction.Declaration
Swift
public func insert<C>(contentsOf newElements: C, at i: Int) where Element == C.Element, C : Collection
-
Removes objects from the list at the given range.
Warning
This method may only be called during a write transaction.Declaration
Swift
public func removeSubrange<R>(_ boundsExpression: R) where R : RangeExpression, R.Bound == Int
-
Returns the minimum (lowest) value in the list, or
nil
if the list is empty.Declaration
Swift
public func min() -> Element?
-
Returns the maximum (highest) value in the list, or
nil
if the list is empty.Declaration
Swift
public func max() -> Element?
-
Returns the sum of the values in the list.
Declaration
Swift
public func sum() -> Element
-
Returns the average of the values in the list, or
nil
if the list is empty.Declaration
Swift
public func average() -> Double?
-
Declaration
Swift
public convenience init(from decoder: Decoder) throws
-
Declaration
Swift
public func encode(to encoder: Encoder) throws
-
Returns the Permission object for the named Role in this List, creating it if needed.
This function should be used in preference to manually querying the List for the applicable Permission as it ensures that there is exactly one Permission for the given Role, merging duplicates and inserting new ones as needed.
Warning
This can only be called on a managed List. Warning
The managing Realm must be in a write transaction.
Declaration
Swift
public func findOrCreate(forRoleNamed roleName: String) -> Permission
Parameters
roleName
The name of the Role to obtain the Permission for.
Return Value
A Permission object contained in this List for the named Role.
-
Returns the Permission object for the named Role in this List, creating it if needed.
This function should be used in preference to manually querying the List for the applicable Permission as it ensures that there is exactly one Permission for the given Role, merging duplicates and inserting new ones as needed.
Warning
This can only be called on a managed List. Warning
The managing Realm must be in a write transaction.
Declaration
Swift
public func findOrCreate(forRole role: PermissionRole) -> Permission
Parameters
roleName
The name of the Role to obtain the Permission for.
Return Value
A Permission object contained in this List for the named Role.