Generic Structure

EmptyCollection

A collection whose element type is Element but that is always empty.

Declaration

@frozen struct EmptyCollection<Element>

Topics

Type Aliases

typealias EmptyCollection.Regions
typealias EmptyCollection.Index

A type that represents a valid position in the collection.

typealias EmptyCollection.Indices

A type that represents the indices that are valid for subscripting the collection, in ascending order.

typealias EmptyCollection.SubSequence

A sequence that represents a contiguous subrange of the collection’s elements.

Initializers

init()

Creates an instance.

Instance Properties

var count: Int

The number of elements (always zero).

var endIndex: EmptyCollection<Element>.Index

Always zero, just like startIndex.

var first: Element?

The first element of the collection.

var indices: Range<Int>

The indices that are valid for subscripting the collection, in ascending order.

var isEmpty: Bool

A Boolean value indicating whether the collection is empty.

var last: Element?

The last element of the collection.

var lazy: LazySequence<EmptyCollection<Element>>

A sequence containing the same elements as this sequence, but on which some operations, such as map and filter, are implemented lazily.

var regions: EmptyCollection<Data>
var startIndex: EmptyCollection<Element>.Index

Always zero, just like endIndex.

var underestimatedCount: Int

A value less than or equal to the number of elements in the collection.

Instance Methods

func allSatisfy((Element) -> Bool) -> Bool

Returns a Boolean value indicating whether every element of a sequence satisfies a given predicate.

func compactMap<ElementOfResult>((Element) -> ElementOfResult?) -> [ElementOfResult]

Returns an array containing the non-nil results of calling the given transformation with each element of this sequence.

func contains(Element) -> Bool

Returns a Boolean value indicating whether the sequence contains the given element.

func contains(where: (Element) -> Bool) -> Bool

Returns a Boolean value indicating whether the sequence contains an element that satisfies the given predicate.

func difference<C>(from: C) -> CollectionDifference<Element>

Returns the difference needed to produce this collection’s ordered elements from the given collection.

func difference<C>(from: C, by: (C.Element, Element) -> Bool) -> CollectionDifference<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: (Element) -> Bool) -> EmptyCollection<Element>

Returns a subsequence by skipping elements while predicate returns true and returning the remaining elements.

func dropFirst(Int) -> EmptyCollection<Element>

Returns a subsequence containing all but the given number of initial elements.

func dropLast(Int) -> EmptyCollection<Element>

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: (Element, 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<EmptyCollection<Element>>

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((Element) -> Bool) -> [Element]

Returns an array containing, in order, the elements of the sequence that satisfy the given predicate.

func first(where: (Element) -> Bool) -> Element?

Returns the first element of the sequence that satisfies the given predicate.

func firstIndex(of: Element) -> Int?

Returns the first index where the specified value appears in the collection.

func firstIndex(where: (Element) -> Bool) -> Int?

Returns the first index in which an element of the collection satisfies the given predicate.

func flatMap<SegmentOfResult>((Element) -> SegmentOfResult) -> [SegmentOfResult.Element]

Returns an array containing the concatenated results of calling the given transformation with each element of this sequence.

func forEach((Element) -> Void)

Calls the given closure on each element in the sequence in the same order as a for-in loop.

func formIndex(inout Int, offsetBy: Int)

Offsets the given index by the specified distance.

func formIndex(inout Int, offsetBy: Int, limitedBy: Int) -> Bool

Offsets the given index by the specified distance, or so that it equals the given limiting index.

func formIndex(after: inout Int)

Replaces the given index with its successor.

func formIndex(before: inout Int)

Replaces the given index with its predecessor.

func index(EmptyCollection<Element>.Index, offsetBy: Int) -> EmptyCollection<Element>.Index

Returns an index that is the specified distance from the given index.

func index(EmptyCollection<Element>.Index, offsetBy: Int, limitedBy: EmptyCollection<Element>.Index) -> EmptyCollection<Element>.Index?

Returns an index that is the specified distance from the given index, unless that distance is beyond a given limiting index.

func index(of: Element) -> Int?

Returns the first index where the specified value appears in the collection.

Deprecated
func index(where: (Element) -> Bool) -> Int?

Returns the first index in which an element of the collection satisfies the given predicate.

Deprecated
func joined() -> FlattenSequence<EmptyCollection<Element>>

Returns the elements of this sequence of sequences, concatenated.

func joined<Separator>(separator: Separator) -> JoinedSequence<EmptyCollection<Element>>

Returns the concatenated elements of this sequence of sequences, inserting the given separator between each element.

func joined(separator: String) -> String

Returns a new string by concatenating the elements of the sequence, adding the given separator between each element.

func joined(separator: String) -> String

Returns a new string by concatenating the elements of the sequence, adding the given separator between each element.

func last(where: (Element) -> Bool) -> Element?

Returns the last element of the sequence that satisfies the given predicate.

func lastIndex(of: Element) -> Int?

Returns the last index where the specified value appears in the collection.

func lastIndex(where: (Element) -> Bool) -> Int?

Returns the index of the last element in the collection that matches the given predicate.

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: (Element, Element) -> Bool) -> Bool

Returns a Boolean value indicating whether the sequence precedes another sequence in a lexicographical (dictionary) ordering, using the given predicate to compare elements.

func map<T>((Element) -> T) -> [T]

Returns an array containing the results of mapping the given closure over the sequence’s elements.

func max() -> Element?

Returns the maximum element in the sequence.

func max(by: (Element, Element) -> Bool) -> Element?

Returns the maximum element in the sequence, using the given predicate as the comparison between elements.

func min() -> Element?

Returns the minimum element in the sequence.

func min(by: (Element, Element) -> Bool) -> Element?

Returns the minimum element in the sequence, using the given predicate as the comparison between elements.

func partition(by: (Element) -> Bool) -> Int

Reorders 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 popFirst() -> Element?

Removes and returns the first element of the collection.

func popLast() -> Element?

Removes and returns the last element of the collection.

func prefix(Int) -> EmptyCollection<Element>

Returns a subsequence, up to the specified maximum length, containing the initial elements of the collection.

func prefix(through: Int) -> EmptyCollection<Element>

Returns a subsequence from the start of the collection through the specified position.

func prefix(upTo: Int) -> EmptyCollection<Element>

Returns a subsequence from the start of the collection up to, but not including, the specified position.

func prefix(while: (Element) -> Bool) -> EmptyCollection<Element>

Returns a subsequence containing the initial elements until predicate returns false and skipping the remaining elements.

func randomElement() -> Element?

Returns a random element of the collection.

func randomElement<T>(using: inout T) -> Element?

Returns a random element of the collection, using the given generator as a source for randomness.

func reduce<Result>(Result, (Result, Element) -> Result) -> Result

Returns the result of combining the elements of the sequence using the given closure.

func reduce<Result>(into: Result, (inout Result, Element) -> ()) -> Result

Returns the result of combining the elements of the sequence using the given closure.

func removeFirst() -> Element

Removes and returns the first element of the collection.

func removeFirst(Int)

Removes the specified number of elements from the beginning of the collection.

func removeLast() -> Element

Removes and returns the last element of the collection.

func removeLast(Int)

Removes the given number of elements from the end of the collection.

func reverse()

Reverses the elements of the collection in place.

func reversed() -> ReversedCollection<EmptyCollection<Element>>

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() -> [Element]

Returns the elements of the sequence, shuffled.

func shuffled<T>(using: inout T) -> [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: (Element, Element) -> Bool)

Sorts the collection in place, using the given predicate as the comparison between elements.

func sorted() -> [Element]

Returns the elements of the sequence, sorted.

func sorted(by: (Element, Element) -> Bool) -> [Element]

Returns the elements of the sequence, sorted using the given predicate as the comparison between elements.

func split(maxSplits: Int, omittingEmptySubsequences: Bool, whereSeparator: (Element) -> Bool) -> [EmptyCollection<Element>]

Returns the longest possible subsequences of the collection, in order, that don’t contain elements satisfying the given predicate.

func split(separator: Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [EmptyCollection<Element>]

Returns the longest possible subsequences of the collection, in order, around elements equal to the given element.

func split(separator: Element, maxSplits: Int, omittingEmptySubsequences: Bool) -> [ArraySlice<Element>]

Returns the longest possible subsequences of the sequence, 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: (Element, 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) -> EmptyCollection<Element>

Returns a subsequence, up to the given maximum length, containing the final elements of the collection.

func suffix(from: Int) -> EmptyCollection<Element>

Returns a subsequence from the specified position to the end of the collection.

func swapAt(Int, Int)

Exchanges the values at the specified indices of the collection.

func withContiguousMutableStorageIfAvailable<R>((inout UnsafeMutableBufferPointer<Element>) -> R) -> R?

Call body(p), where p is a pointer to the collection’s mutable contiguous storage. If no such storage exists, it is first created. If the collection does not support an internal representation in a form of mutable contiguous storage, body is not called and nil is returned.

func withContiguousStorageIfAvailable<R>((UnsafeBufferPointer<Element>) -> 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(EmptyCollection<Element>.Index) -> Element

Accesses the element at the given position.

subscript(Range<EmptyCollection<Element>.Index>) -> EmptyCollection<Element>.SubSequence

Accesses a contiguous subrange of the collection’s elements.

subscript(Range<Int>) -> Slice<EmptyCollection<Element>>

Accesses a contiguous subrange of the collection’s elements.

subscript<R>(R) -> EmptyCollection<Element>

Accesses the contiguous subrange of the collection’s elements specified by a range expression.

Operator Functions

static func != (EmptyCollection<Element>, EmptyCollection<Element>) -> Bool

Returns a Boolean value indicating whether two values are not equal.

static func == (EmptyCollection<Element>, EmptyCollection<Element>) -> Bool

Returns a Boolean value indicating whether two values are equal.

Structures

struct EmptyCollection.Iterator

An iterator that never produces an element.

Relationships

Conforms To

See Also

Special-Use Collections

func repeatElement<T>(T, count: Int) -> Repeated<T>

Creates a collection containing the specified number of the given element.

struct CollectionOfOne

A collection containing a single element.

struct KeyValuePairs

A lightweight collection of key-value pairs.

Beta Software

This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.

Learn more about using Apple's beta software