Results

public final class Results<Element: RealmCollectionValue>: NSObject, NSFastEnumeration

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 override var description: String
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Fast Enumeration

  • The type of the objects described by the results.

    Declaration

    Swift

    public typealias ElementType = Element
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Properties

  • The Realm which manages this results. Note that this property will never return nil.

    Declaration

    Swift

    public var realm: Realm?
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  • Indicates if the results are no longer valid.

    The results becomes invalid if invalidate() is called on the containing realm. An invalidated results can be accessed, but will always be empty.

    Declaration

    Swift

    public var isInvalidated: Bool
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  • The number of objects in the results.

    Declaration

    Swift

    public var count: Int
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Index Retrieval

  • 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?
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  • 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.
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  • 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.
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Object Retrieval

  • Returns the object at the given index.

    Declaration

    Swift

    public subscript(position: Int) -> Element

    Parameters

    index

    The index.
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  • Returns the first object in the results, or nil if the results are empty.

    Declaration

    Swift

    public var first: Element?
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  • Returns the last object in the results, or nil if the results are empty.

    Declaration

    Swift

    public var last: Element?
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KVC

  • Returns an Array containing the results of invoking valueForKey(_:) with key on each of the results.

    Declaration

    Swift

    public override func value(forKey key: String) -> Any?

    Parameters

    key

    The name of the property whose values are desired.
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  • Returns an Array containing the results of invoking valueForKeyPath(_:) with keyPath on each of the results.

    Declaration

    Swift

    public override func value(forKeyPath keyPath: String) -> Any?

    Parameters

    keyPath

    The key path to the property whose values are desired.
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  • Invokes setValue(_:forKey:) on each of the objects represented by the results using the specified value and key.

    Warning

    This method may 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.
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Filtering

  • 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.
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  • 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.
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Sorting

  • 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 Students from youngest to oldest based on their age property, you might call students.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.
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  • 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.

    See

    sorted(byKeyPath:ascending:)

    Declaration

    Swift

    public func sorted<S: Sequence>(by sortDescriptors: S) -> Results<Element>
        where S.Iterator.Element == SortDescriptor

    Parameters

    sortDescriptors

    A sequence of SortDescriptors to sort by.
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  • Returns a Results containing distinct objects based on the specified key paths

    Declaration

    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
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Aggregate Operations

  • 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: MinMaxType>(ofProperty property: String) -> T?

    Parameters

    property

    The name of a property whose minimum value is desired.
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  • 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: MinMaxType>(ofProperty property: String) -> T?

    Parameters

    property

    The name of a property whose minimum value is desired.
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  • 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: AddableType>(ofProperty property: String) -> T

    Parameters

    property

    The name of a property whose values should be summed.
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  • 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: AddableType>(ofProperty property: String) -> T?

    Parameters

    property

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

  • 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 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 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 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(_ 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.

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Sequence Support

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
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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
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  • Declaration

    Swift

    public func index(after i: Int) -> Int

    Parameters

    i
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  • Declaration

    Swift

    public func index(before i: Int) -> Int

    Parameters

    i
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