Results
public struct Results<Element> : Equatable where Element : RealmCollectionValue
Results
is an auto-updating container type in Realm returned from object queries.
Results
can be queried with the same predicates as List<Element>
, and you can
chain queries to further filter query results.
Results
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 objects which matched the query when the enumeration is begun, even if some of them are deleted or modified to be
excluded by the filter during the enumeration.
Results
are lazily evaluated the first time they are accessed; they only run queries when the result of the query is
requested. This means that chaining several temporary Results
to sort and filter your data does not perform any
unnecessary work processing the intermediate state.
Once the results have been evaluated or a notification block has been added, the results are eagerly kept up-to-date, with the work done to keep them up-to-date done on a background thread whenever possible.
Results instances cannot be directly instantiated.
-
A human-readable description of the objects represented by the results.
Declaration
Swift
public var description: String { get }
-
The type of the objects described by the results.
Declaration
Swift
public typealias ElementType = Element
-
The Realm which manages this results. Note that this property will never return
nil
.Declaration
Swift
public var realm: Realm? { get }
-
Indicates if the results are no longer valid.
The results becomes invalid if
invalidate()
is called on the containingrealm
. An invalidated results can be accessed, but will always be empty.Declaration
Swift
public var isInvalidated: Bool { get }
-
The number of objects in the results.
Declaration
Swift
public var count: Int { get }
-
Returns the index of the given object in the results, or
nil
if the object is not present.Declaration
Swift
public func index(of object: Element) -> Int?
-
Returns the index of the first object 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 index of the first object matching the predicate, or
nil
if no objects match.Declaration
Swift
public func index(matching predicateFormat: String, _ args: Any...) -> Int?
Parameters
predicateFormat
A predicate format string, optionally followed by a variable number of arguments.
-
Returns the object at the given
index
.Declaration
Swift
public subscript(position: Int) -> Element { get }
Parameters
index
The index.
-
Returns the first object in the results, or
nil
if the results are empty.Declaration
Swift
public var first: Element? { get }
-
Returns the last object in the results, or
nil
if the results are empty.Declaration
Swift
public var last: Element? { get }
-
Returns an
Array
containing the results of invokingvalueForKey(_:)
withkey
on each of the results.Declaration
Swift
public func value(forKey key: String) -> Any?
Parameters
key
The name of the property whose values are desired.
-
Returns an
Array
containing the results of invokingvalueForKeyPath(_:)
withkeyPath
on each of the results.Declaration
Swift
public func value(forKeyPath keyPath: String) -> Any?
Parameters
keyPath
The key path to the property whose values are desired.
-
Invokes
setValue(_:forKey:)
on each of the objects represented by the results using the specifiedvalue
andkey
.Warning
This method may only be called during a write transaction.
Declaration
Swift
public 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 all objects matching the given predicate in the collection.Declaration
Swift
public func filter(_ predicateFormat: String, _ args: Any...) -> Results<Element>
Parameters
predicateFormat
A predicate format string, optionally followed by a variable number of arguments.
-
Returns a
Results
containing all objects matching the given predicate in the collection.Declaration
Swift
public func filter(_ predicate: NSPredicate) -> Results<Element>
Parameters
predicate
The predicate with which to filter the objects.
-
Returns a
Results
containing the objects represented by the results, but sorted.Objects are sorted based on the values of the given key path. For example, to sort a collection of
Student
s from youngest to oldest based on theirage
property, you might callstudents.sorted(byKeyPath: "age", ascending: true)
.Warning
Collections 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 represented by the results, but sorted.Warning
Collections 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
Parameters
sortDescriptors
A sequence of
SortDescriptor
s to sort by. -
Returns a
Results
containing distinct objects based on the specified key pathsDeclaration
Swift
public func distinct<S: Sequence>(by keyPaths: S) -> Results<Element> where S.Iterator.Element == String
Parameters
keyPaths
The key paths used produce distinct results
-
Returns the minimum (lowest) value of the given property among all the results, or
nil
if the results are 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 results, or
nil
if the results are 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 minimum value is desired.
-
Returns the sum of the values of a given property over all the results.
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 results, or
nil
if the results are empty.Warning
Only the name of 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.
-
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.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 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 dogs = 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(_ block: @escaping (RealmCollectionChange<Results>) -> Void) -> NotificationToken
Parameters
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.
-
Returns a
RLMIterator
that yields successive elements in the results.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
-
Declaration
Swift
public func encode(to encoder: Encoder) throws
-
Subscribe to the query represented by this
Results
Subscribing to a query asks the server to synchronize all objects to the client which match the query, along with all objects which are reachable from those objects via links. This happens asynchronously, and the local client Realm may not immediately have all objects which match the query. Observe the
state
property of the returned subscription object to be notified of when the subscription has been processed by the server and all objects matching the query are available.
Creating a new subscription with the same name and query as an existing subscription will not create a new subscription, but instead will return an object referring to the existing sync subscription. This means that performing the same subscription twice followed by removing it once will result in no subscription existing.
By default trying to create a subscription with a name as an existing subscription with a different query or options will fail. If
update
istrue
, instead the existing subscription will be changed to use the query and options from the new subscription. This only works if the new subscription is for the same type of objects as the existing subscription, and trying to overwrite a subscription with a subscription of a different type of objects will still fail.
The number of top-level objects which are included in the subscription can optionally be limited by setting the
limit
paramter. If more top-level objects than the limit match the query, only the firstlimit
objects will be included. This respects the sort and distinct order of the query being subscribed to for the determination of what thefirst
objects are.The limit does not count or apply to objects which are added indirectly due to being linked to by the objects in the subscription or due to being listed in
includeLinkingObjects
. If the limit is larger than the number of objects which match the query, all objects will be included.
By default subscriptions are persistent, and last until they are explicitly removed by calling
unsubscribe()
. Subscriptions can instead be made temporary by setting the time to live to how long the subscription should remain. After that time has elapsed the subscription will be automatically removed.
Outgoing links (i.e.
List
andObject
properties) are automatically included in sync subscriptions. That is, if you subscribe to a query which matches one object, every object which is reachable via links from that object are also included in the subscription. By default,LinkingObjects
properties do not work this way and instead, they only report objects which happen to be included in a subscription. SpecificLinkingObjects
properties can be explicitly included in the subscription by naming them in theincludingLinkingObjects
array. Any keypath which ends in aLinkingObjects
property can be included in this array, including ones involving intermediate links.
Creating a subscription is an asynchronous operation and the newly created subscription will not be reported by Realm.subscriptions() until it has transitioned from the
.creating
state to.pending
,.created
or.error
.Declaration
Swift
public func subscribe(named subscriptionName: String? = nil, limit: Int? = nil, update: Bool = false, timeToLive: TimeInterval? = nil, includingLinkingObjects: [String] = []) -> SyncSubscription
Parameters
subscriptionName
An optional name for the subscription.
limit
The maximum number of top-level objects to include in the subscription.
update
Whether an existing subscription with the same name should be updated or if it should be an error.
timeToLive
How long in seconds this subscription should remain active.
includingLinkingObjects
Which
LinkingObjects
properties should pull in the contained objects.Return Value
The subscription.