A collection containing a single element.
@frozen struct CollectionOfOne<Element>You can use a CollectionOfOne instance when you need to efficiently represent a single value as a collection. For example, you can add a single element to an array by using a CollectionOfOne instance with the concatenation operator (+):
let a = [1, 2, 3, 4]
let toAdd = 100
let b = a + CollectionOfOne(toAdd)
// b == [1, 2, 3, 4, 100]typealias IndexA type that represents a position in the collection.
typealias IndicesA type that represents the indices that are valid for subscripting the collection, in ascending order.
typealias SubSequenceA collection representing a contiguous subrange of this collection’s elements. The subsequence shares indices with the original collection.
init(Element)Creates an instance containing just the given element.
subscript((UnboundedRange_) -> ()) -> Self.SubSequencesubscript(Range<Self.Index>) -> Slice<Self>Accesses a contiguous subrange of the collection’s elements.
subscript<R>(R) -> Self.SubSequenceAccesses the contiguous subrange of the collection’s elements specified by a range expression.
subscript(Int) -> ElementAccesses the element at the specified position.
subscript(Range<Int>) -> CollectionOfOne<Element>.SubSequenceAccesses a contiguous subrange of the collection’s elements.
<unavailable>subscript<R>(R) -> Self.SubSequencesubscript(Range<Self.Index>) -> Slice<Self>Accesses a contiguous subrange of the collection’s elements.
subscript((UnboundedRange_) -> ()) -> Self.SubSequence<unavailable>var count: IntThe number of elements in the collection.
var count: IntThe number of elements in the collection, which is always one.
var customMirror: MirrorThe custom mirror for this instance.
var debugDescription: StringA textual representation of the collection, suitable for debugging.
var endIndex: CollectionOfOne<Element>.IndexThe “past the end” position—that is, the position one greater than the last valid subscript argument.
var first: Self.Element?The first element of the collection.
var isEmpty: BoolA Boolean value indicating whether the collection is empty.
var last: Self.Element?The last element of the collection.
var lazy: LazySequence<Self>A sequence containing the same elements as this sequence, but on which some operations, such as map and filter, are implemented lazily.
var startIndex: CollectionOfOne<Element>.IndexThe position of the first element.
var underestimatedCount: IntA value less than or equal to the number of elements in the collection.
var underestimatedCount: IntA value less than or equal to the number of elements in the sequence, calculated nondestructively.
func allSatisfy((Self.Element) throws -> Bool) rethrows -> BoolReturns a Boolean value indicating whether every element of a sequence satisfies a given predicate.
func compactMap<ElementOfResult>((Self.Element) throws -> ElementOfResult?) rethrows -> [ElementOfResult]Returns an array containing the non-nil results of calling the given transformation with each element of this sequence.
func contains(Self.Element) -> BoolReturns a Boolean value indicating whether the sequence contains the given element.
func contains(where: (Self.Element) throws -> Bool) rethrows -> BoolReturns a Boolean value indicating whether the sequence contains an element that satisfies the given predicate.
func difference<C>(from: C) -> CollectionDifference<Self.Element>Returns the difference needed to produce this collection’s ordered elements from the given collection.
func difference<C>(from: C, by: (C.Element, Self.Element) -> Bool) -> CollectionDifference<Self.Element>Returns the difference needed to produce this collection’s ordered elements from the given collection, using the given predicate as an equivalence test.
func drop(while: (Self.Element) throws -> Bool) rethrows -> Self.SubSequenceReturns a subsequence by skipping elements while predicate returns true and returning the remaining elements.
func dropFirst(Int) -> Self.SubSequenceReturns a subsequence containing all but the given number of initial elements.
func dropLast(Int) -> Self.SubSequenceReturns a subsequence containing all but the specified number of final elements.
func elementsEqual<OtherSequence>(OtherSequence) -> BoolReturns a Boolean value indicating whether this sequence and another sequence contain the same elements in the same order.
func elementsEqual<OtherSequence>(OtherSequence, by: (Self.Element, OtherSequence.Element) throws -> Bool) rethrows -> BoolReturns 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<Self>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((Self.Element) throws -> Bool) rethrows -> [Self.Element]Returns an array containing, in order, the elements of the sequence that satisfy the given predicate.
func first(where: (Self.Element) throws -> Bool) rethrows -> Self.Element?Returns the first element of the sequence that satisfies the given predicate.
func firstIndex(of: Self.Element) -> Self.Index?Returns the first index where the specified value appears in the collection.
func firstIndex(where: (Self.Element) throws -> Bool) rethrows -> Self.Index?Returns the first index in which an element of the collection satisfies the given predicate.
func flatMap<SegmentOfResult>((Self.Element) throws -> SegmentOfResult) rethrows -> [SegmentOfResult.Element]Returns an array containing the concatenated results of calling the given transformation with each element of this sequence.
func forEach((Self.Element) throws -> Void) rethrowsCalls the given closure on each element in the sequence in the same order as a for-in loop.
func formIndex(inout Self.Index, offsetBy: Int)Offsets the given index by the specified distance.
func formIndex(inout Self.Index, offsetBy: Int, limitedBy: Self.Index) -> BoolOffsets the given index by the specified distance, or so that it equals the given limiting index.
func formIndex(after: inout Self.Index)Replaces the given index with its successor.
func formIndex(before: inout Self.Index)Replaces the given index with its predecessor.
func index(Self.Index, offsetBy: Int, limitedBy: Self.Index) -> Self.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: CollectionOfOne<Element>.Index) -> CollectionOfOne<Element>.IndexReturns the position immediately after the given index.
func index(before: CollectionOfOne<Element>.Index) -> CollectionOfOne<Element>.IndexReturns the position immediately before the given index.
func joined() -> FlattenSequence<Self>Returns the elements of this sequence of sequences, concatenated.
func joined(separator: String) -> StringReturns a new string by concatenating the elements of the sequence, adding 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 joined<Separator>(separator: Separator) -> JoinedSequence<Self>Returns the concatenated elements of this sequence of sequences, inserting the given separator between each element.
func last(where: (Self.Element) throws -> Bool) rethrows -> Self.Element?Returns the last element of the sequence that satisfies the given predicate.
func lastIndex(of: Self.Element) -> Self.Index?Returns the last index where the specified value appears in the collection.
func lastIndex(where: (Self.Element) throws -> Bool) rethrows -> Self.Index?Returns the index of the last element in the collection that matches the given predicate.
func lexicographicallyPrecedes<OtherSequence>(OtherSequence) -> BoolReturns 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: (Self.Element, Self.Element) throws -> Bool) rethrows -> 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() -> CollectionOfOne<Element>.IteratorReturns an iterator over the elements of this collection.
func map<T>((Self.Element) throws -> T) rethrows -> [T]Returns an array containing the results of mapping the given closure over the sequence’s elements.
func map<T>((Self.Element) throws -> T) rethrows -> [T]Returns an array containing the results of mapping the given closure over the sequence’s elements.
func max() -> Self.Element?Returns the maximum element in the sequence.
func max(by: (Self.Element, Self.Element) throws -> Bool) rethrows -> Self.Element?Returns the maximum element in the sequence, using the given predicate as the comparison between elements.
func min() -> Self.Element?Returns the minimum element in the sequence.
func min(by: (Self.Element, Self.Element) throws -> Bool) rethrows -> Self.Element?Returns the minimum element in the sequence, using the given predicate as the comparison between elements.
func partition(by: (Self.Element) throws -> Bool) rethrows -> Self.IndexReorders the elements of the collection such that all the elements that match the given predicate are after all the elements that don’t match.
func partition(by: (Self.Element) throws -> Bool) rethrows -> Self.IndexReorders the elements of the collection such that all the elements that match the given predicate are after all the elements that don’t match.
func prefix(Int) -> Self.SubSequenceReturns a subsequence, up to the specified maximum length, containing the initial elements of the collection.
func prefix(through: Self.Index) -> Self.SubSequenceReturns a subsequence from the start of the collection through the specified position.
func prefix(upTo: Self.Index) -> Self.SubSequenceReturns a subsequence from the start of the collection up to, but not including, the specified position.
func prefix(while: (Self.Element) throws -> Bool) rethrows -> Self.SubSequenceReturns a subsequence containing the initial elements until predicate returns false and skipping the remaining elements.
func randomElement() -> Self.Element?Returns a random element of the collection.
func randomElement<T>(using: inout T) -> Self.Element?Returns a random element of the collection, using the given generator as a source for randomness.
func reduce<Result>(Result, (Result, Self.Element) throws -> Result) rethrows -> ResultReturns the result of combining the elements of the sequence using the given closure.
func reduce<Result>(into: Result, (inout Result, Self.Element) throws -> ()) rethrows -> ResultReturns the result of combining the elements of the sequence using the given closure.
func reverse()Reverses the elements of the collection in place.
func reversed() -> ReversedCollection<Self>Returns a view presenting the elements of the collection in reverse order.
func shuffle()Shuffles the collection in place.
func shuffle<T>(using: inout T)Shuffles the collection in place, using the given generator as a source for randomness.
func shuffled() -> [Self.Element]Returns the elements of the sequence, shuffled.
func shuffled<T>(using: inout T) -> [Self.Element]Returns the elements of the sequence, shuffled using the given generator as a source for randomness.
func sort()Sorts the collection in place.
func sort(by: (Self.Element, Self.Element) throws -> Bool) rethrowsSorts the collection in place, using the given predicate as the comparison between elements.
func sorted() -> [Self.Element]Returns the elements of the sequence, sorted.
func sorted(by: (Self.Element, Self.Element) throws -> Bool) rethrows -> [Self.Element]Returns the elements of the sequence, sorted using the given predicate as the comparison between elements.
func split(maxSplits: Int, omittingEmptySubsequences: Bool, whereSeparator: (Self.Element) throws -> Bool) rethrows -> [Self.SubSequence]Returns the longest possible subsequences of the collection, in order, that don’t contain elements satisfying the given predicate.
func split(separator: Self.Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [Self.SubSequence]Returns the longest possible subsequences of the collection, in order, around elements equal to the given element.
func split(separator: Self.Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [ArraySlice<Self.Element>]Returns the longest possible subsequences of the sequence, in order, around elements equal to the given element.
func starts<PossiblePrefix>(with: PossiblePrefix) -> BoolReturns 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: (Self.Element, PossiblePrefix.Element) throws -> Bool) rethrows -> BoolReturns 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) -> Self.SubSequenceReturns a subsequence, up to the given maximum length, containing the final elements of the collection.
func suffix(from: Self.Index) -> Self.SubSequenceReturns a subsequence from the specified position to the end of the collection.
func swapAt(Self.Index, Self.Index)Exchanges the values at the specified indices of the collection.
func withContiguousMutableStorageIfAvailable<R>((inout UnsafeMutableBufferPointer<Self.Element>) throws -> R) rethrows -> R?Executes a closure on the collection’s contiguous storage.
func withContiguousStorageIfAvailable<R>((UnsafeBufferPointer<Self.Element>) throws -> R) rethrows -> R?Executes a closure on the sequence’s contiguous storage.
func withUnsafeBytes<R>((UnsafeRawBufferPointer) throws -> R) rethrows -> RCalls the given closure with the contents of underlying storage.
struct IteratorAn iterator that produces one or zero instances of an element.
func flatMap<ElementOfResult>((Self.Element) throws -> ElementOfResult?) rethrows -> [ElementOfResult]func index(of: Self.Element) -> Self.Index?Returns the first index where the specified value appears in the collection.