A view of a dictionary’s keys.
SDK
- Xcode 9.0+
Framework
- Swift Standard Library
Declaration
@frozen struct Keys
StructureDictionary
Dictionary.Keys
Topics
Type Aliases
typealias Dictionary.Keys.Element A type representing the sequence’s elements.
typealias Dictionary.Keys.Index A type that represents a position in the collection.
typealias Dictionary.Keys.Indices A type that represents the indices that are valid for subscripting the collection, in ascending order.
typealias Dictionary.Keys.SubSequence A sequence that represents a contiguous subrange of the collection’s elements.
Instance Properties
var count: IntThe number of keys in the dictionary.
var debugDescription : StringA textual representation of this instance, suitable for debugging.
var description: StringA textual representation of this instance.
var endIndex : Dictionary<Key, Value>.IndexThe collection’s “past the end” position—that is, the position one greater than the last valid subscript argument.
var first: Key?The first element of the collection.
var indices: DefaultIndices<Dictionary<Key, Value>.Keys> The indices that are valid for subscripting the collection, in ascending order.
var isEmpty : BoolA Boolean value indicating whether the collection is empty.
var lazy: LazySequence<Dictionary<Key, Value>.Keys> A sequence containing the same elements as this sequence, but on which some operations, such as map and filter, are implemented lazily.
var startIndex : Dictionary<Key, Value>.IndexThe position of the first element in a nonempty collection.
var underestimatedCount : IntA value less than or equal to the number of elements in the collection.
Instance Methods
func allSatisfy ((Key) -> Bool) -> BoolReturns a Boolean value indicating whether every element of a sequence satisfies a given predicate.
func compactMap <ElementOfResult>((Key) -> ElementOfResult?) -> [ElementOfResult] Returns an array containing the non-nil results of calling the given transformation with each element of this sequence.
func contains(Key) -> BoolReturns a Boolean value indicating whether the sequence contains the given element.
func contains(where: (Key) -> Bool) -> BoolReturns a Boolean value indicating whether the sequence contains an element that satisfies the given predicate.
func distance(from: Dictionary<Key, Value>.Index, to: Dictionary<Key, Value>.Index) -> IntReturns the distance between two indices.
func drop(while: (Key) -> Bool) -> Slice<Dictionary<Key, Value>.Keys>Returns a subsequence by skipping elements while predicate returns true and returning the remaining elements.
func dropFirst (Int) -> Slice<Dictionary<Key, Value>.Keys>Returns a subsequence containing all but the given number of initial elements.
func dropLast (Int) -> Slice<Dictionary<Key, Value>.Keys>Returns a subsequence containing all but the specified number of final elements.
func elementsEqual <OtherSequence>(OtherSequence) -> Bool Returns a Boolean value indicating whether this sequence and another sequence contain the same elements in the same order.
func elementsEqual <OtherSequence>(OtherSequence, by: (Key, OtherSequence.Element) -> Bool) -> Bool Returns a Boolean value indicating whether this sequence and another sequence contain equivalent elements in the same order, using the given predicate as the equivalence test.
func enumerated() -> EnumeratedSequence<Dictionary<Key, Value>.Keys> Returns a sequence of pairs (n, x), where n represents a consecutive integer starting at zero and x represents an element of the sequence.
func filter((Key) -> Bool) -> [Key]Returns an array containing, in order, the elements of the sequence that satisfy the given predicate.
func first(where: (Key) -> Bool) -> Key?Returns the first element of the sequence that satisfies the given predicate.
func firstIndex (of: Key) -> Dictionary<Key, Value>.Index?Returns the first index where the specified value appears in the collection.
func firstIndex (where: (Key) -> Bool) -> Dictionary<Key, Value>.Index?Returns the first index in which an element of the collection satisfies the given predicate.
func flatMap <SegmentOfResult>((Key) -> SegmentOfResult) -> [SegmentOfResult.Element] Returns an array containing the concatenated results of calling the given transformation with each element of this sequence.
func forEach ((Key) -> Void)Calls the given closure on each element in the sequence in the same order as a for-in loop.
func formIndex (inout Dictionary<Key, Value>.Index, offsetBy : Int)Offsets the given index by the specified distance.
func formIndex (inout Dictionary<Key, Value>.Index, offsetBy : Int, limitedBy : Dictionary<Key, Value>.Index) -> BoolOffsets the given index by the specified distance, or so that it equals the given limiting index.
func formIndex (after: inout Dictionary<Key, Value>.Index)Replaces the given index with its successor.
func index(Dictionary<Key, Value>.Index, offsetBy : Int) -> Dictionary<Key, Value>.IndexReturns an index that is the specified distance from the given index.
func index(Dictionary<Key, Value>.Index, offsetBy : Int, limitedBy : Dictionary<Key, Value>.Index) -> Dictionary<Key, Value>.Index?Returns an index that is the specified distance from the given index, unless that distance is beyond a given limiting index.
func index(after: Dictionary<Key, Value>.Index) -> Dictionary<Key, Value>.IndexReturns the position immediately after the given index.
func index(of: Key) -> Dictionary<Key, Value>.Index?Returns the first index where the specified value appears in the collection.
func index(where: (Key) -> Bool) -> Dictionary<Key, Value>.Index?Returns the first index in which an element of the collection satisfies the given predicate.
func joined() -> FlattenSequence<Dictionary<Key, Value>.Keys> Returns the elements of this sequence of sequences, concatenated.
func joined<Separator>(separator: Separator) -> JoinedSequence<Dictionary<Key, Value>.Keys> Returns the concatenated elements of this sequence of sequences, inserting the given separator between each element.
func joined(separator: String) -> StringReturns a new string by concatenating the elements of the sequence, adding the given separator between each element.
func lexicographicallyPrecedes <OtherSequence>(OtherSequence) -> Bool Returns a Boolean value indicating whether the sequence precedes another sequence in a lexicographical (dictionary) ordering, using the less-than operator (<) to compare elements.
func lexicographicallyPrecedes <OtherSequence>(OtherSequence, by: (Key, Key) -> Bool) -> BoolReturns a Boolean value indicating whether the sequence precedes another sequence in a lexicographical (dictionary) ordering, using the given predicate to compare elements.
func makeIterator () -> Dictionary<Key, Value>.Keys.Iterator Returns an iterator over the elements of the collection.
func map<T>((Key) -> T) -> [T]Returns an array containing the results of mapping the given closure over the sequence’s elements.
func max() -> Key?Returns the maximum element in the sequence.
func max(by: (Key, Key) -> Bool) -> Key?Returns the maximum element in the sequence, using the given predicate as the comparison between elements.
func min() -> Key?Returns the minimum element in the sequence.
func min(by: (Key, Key) -> Bool) -> Key?Returns the minimum element in the sequence, using the given predicate as the comparison between elements.
func prefix(Int) -> Slice<Dictionary<Key, Value>.Keys>Returns a subsequence, up to the specified maximum length, containing the initial elements of the collection.
func prefix(through: Dictionary<Key, Value>.Index) -> Slice<Dictionary<Key, Value>.Keys>Returns a subsequence from the start of the collection through the specified position.
func prefix(upTo : Dictionary<Key, Value>.Index) -> Slice<Dictionary<Key, Value>.Keys>Returns a subsequence from the start of the collection up to, but not including, the specified position.
func prefix(while: (Key) -> Bool) -> Slice<Dictionary<Key, Value>.Keys>Returns a subsequence containing the initial elements until predicate returns false and skipping the remaining elements.
func randomElement () -> Key?Returns a random element of the collection.
func randomElement <T>(using: inout T) -> Key?Returns a random element of the collection, using the given generator as a source for randomness.
func reduce<Result>(Result, (Result, Key) -> Result) -> ResultReturns the result of combining the elements of the sequence using the given closure.
func reduce<Result>(into: Result, (inout Result, Key) -> ()) -> ResultReturns the result of combining the elements of the sequence using the given closure.
func reversed() -> [Key]Returns an array containing the elements of this sequence in reverse order.
func shuffled() -> [Key]Returns the elements of the sequence, shuffled.
func shuffled<T>(using: inout T) -> [Key]Returns the elements of the sequence, shuffled using the given generator as a source for randomness.
func sorted() -> [Key]Returns the elements of the sequence, sorted.
func sorted(by: (Key, Key) -> Bool) -> [Key]Returns the elements of the sequence, sorted using the given predicate as the comparison between elements.
func split(maxSplits : Int, omittingEmptySubsequences : Bool, whereSeparator : (Key) -> Bool) -> [Slice<Dictionary<Key, Value>.Keys>]Returns the longest possible subsequences of the collection, in order, that don’t contain elements satisfying the given predicate.
func split(separator: Key, maxSplits : Int, omittingEmptySubsequences : Bool) -> [Slice<Dictionary<Key, Value>.Keys>]Returns the longest possible subsequences of the collection, in order, around elements equal to the given element.
func starts<PossiblePrefix>( with: PossiblePrefix) -> Bool Returns a Boolean value indicating whether the initial elements of the sequence are the same as the elements in another sequence.
func starts<PossiblePrefix>( with: PossiblePrefix, by: (Key, PossiblePrefix.Element) -> Bool) -> Bool Returns a Boolean value indicating whether the initial elements of the sequence are equivalent to the elements in another sequence, using the given predicate as the equivalence test.
func suffix(Int) -> Slice<Dictionary<Key, Value>.Keys>Returns a subsequence, up to the given maximum length, containing the final elements of the collection.
func suffix(from: Dictionary<Key, Value>.Index) -> Slice<Dictionary<Key, Value>.Keys>Returns a subsequence from the specified position to the end of the collection.
func withContiguousStorageIfAvailable <R>((UnsafeBufferPointer<Key>) -> R) -> R? Call body(p), where p is a pointer to the collection’s contiguous storage. If no such storage exists, it is first created. If the collection does not support an internal representation in a form of contiguous storage, body is not called and nil is returned.
Subscripts
subscript(Dictionary<Key, Value>.Index) -> Dictionary<Key, Value>.Keys.Element Accesses the element at the specified position.
subscript(Range<Dictionary<Key, Value>.Index>) -> Slice<Dictionary<Key, Value>.Keys>Accesses a contiguous subrange of the collection’s elements.
subscript<R>(R) -> Slice<Dictionary<Key, Value>.Keys>Accesses the contiguous subrange of the collection’s elements specified by a range expression.
Operator Functions
static func != (Dictionary<Key, Value>.Keys, Dictionary<Key, Value>.Keys) -> BoolReturns a Boolean value indicating whether two values are not equal.
static func == (Dictionary<Key, Value>.Keys, Dictionary<Key, Value>.Keys) -> BoolReturns a Boolean value indicating whether two values are equal.
Structures
struct Dictionary.Keys.Iterator A type that provides the collection’s iteration interface and encapsulates its iteration state.
Relationships
See Also
Supporting Types
struct Dictionary.Values A view of a dictionary’s values.
struct Dictionary.Index The position of a key-value pair in a dictionary.
struct Dictionary.Iterator An iterator over the members of a Dictionary<Key, Value>.