UTF16View
A view of a string’s contents as a collection of UTF-16 code units.
@frozen struct UTF16ViewYou can access a string’s view of UTF-16 code units by using its utf16 property. A string’s UTF-16 view encodes the string’s Unicode scalar values as 16-bit integers.
let flowers = "Flowers 💐"
for v in flowers.utf16 {
print(v)
}
// 70
// 108
// 111
// 119
// 101
// 114
// 115
// 32
// 55357
// 56464Unicode scalar values that make up a string’s contents can be up to 21 bits long. The longer scalar values may need two UInt16 values for storage. Those “pairs” of code units are called surrogate pairs.
let flowermoji = "💐"
for v in flowermoji.unicodeScalars {
print(v, v.value)
}
// 💐 128144
for v in flowermoji.utf16 {
print(v)
}
// 55357
// 56464To convert a String.UTF16View instance back into a string, use the String type’s init(_:) initializer.
let favemoji = "My favorite emoji is 🎉"
if let i = favemoji.utf16.firstIndex(where: { $0 >= 128 }) {
let asciiPrefix = String(favemoji.utf16[..<i])!
print(asciiPrefix)
}
// Prints "My favorite emoji is "UTF16View Elements Match NSString Characters
The UTF-16 code units of a string’s utf16 view match the elements accessed through indexed NSString APIs.
print(flowers.utf16.count)
// Prints "10"
let nsflowers = flowers as NSString
print(nsflowers.length)
// Prints "10"Unlike NSString, however, String.UTF16View does not use integer indices. If you need to access a specific position in a UTF-16 view, use Swift’s index manipulation methods. The following example accesses the fourth code unit in both the flowers and nsflowers strings:
print(nsflowers.character(at: 3))
// Prints "119"
let i = flowers.utf16.index(flowers.utf16.startIndex, offsetBy: 3)
print(flowers.utf16[i])
// Prints "119"Although the Swift overlay updates many Objective-C methods to return native Swift indices and index ranges, some still return instances of NSRange. To convert an NSRange instance to a range of String.Index, use the Range(_:in:) initializer, which takes an NSRange and a string as arguments.
let snowy = "❄️ Let it snow! ☃️"
let nsrange = NSRange(location: 3, length: 12)
if let range = Range(nsrange, in: snowy) {
print(snowy[range])
}
// Prints "Let it snow!"Citizens in Swift
Conformances
protocol BidirectionalCollectionA collection that supports backward as well as forward traversal.
protocol CollectionA sequence whose elements can be traversed multiple times, nondestructively, and accessed by an indexed subscript.
protocol CustomDebugStringConvertibleA type with a customized textual representation suitable for debugging purposes.
protocol CustomReflectableA type that explicitly supplies its own mirror.
protocol CustomStringConvertibleA type with a customized textual representation.
protocol SendableA type whose values can safely be passed across concurrency domains by copying.
protocol SequenceA type that provides sequential, iterated access to its elements.
Members
var count: Intvar customMirror: MirrorReturns a mirror that reflects the UTF-16 view of a string.
var debugDescription: Stringvar description: Stringvar endIndex: String.UTF16View.IndexThe “past the end” position—that is, the position one greater than the last valid subscript argument.
var startIndex: String.UTF16View.IndexThe position of the first code unit if the
Stringis nonempty; identical toendIndexotherwise.subscript(Range<String.UTF16View.Index>) -> Substring.UTF16View subscript(String.UTF16View.Index) -> UTF16.CodeUnit Accesses the code unit at the given position.
func distance(from: String.UTF16View.Index, to: String.UTF16View.Index) -> Int func index(String.UTF16View.Index, offsetBy: Int) -> String.UTF16View.Index func index(String.UTF16View.Index, offsetBy: Int, limitedBy: String.UTF16View.Index) -> String.UTF16View.Index? func index(after: String.UTF16View.Index) -> String.UTF16View.Index func index(before: String.UTF16View.Index) -> String.UTF16View.Index func makeIterator() -> String.UTF16View.Iterator struct Iteratortypealias Indextypealias SubSequencevar customPlaygroundQuickLook: _PlaygroundQuickLook
Features
var first: Self.Element?The first element of the collection.
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
mapandfilter, are implemented lazily.func allSatisfy((Self.Element) throws -> Bool) rethrows -> Bool Returns 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-
nilresults of calling the given transformation with each element of this sequence.func contains(Self.Element) -> Bool Returns a Boolean value indicating whether the sequence contains the given element.
func contains(where: (Self.Element) throws -> Bool) rethrows -> Bool Returns 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.SubSequence Returns a subsequence by skipping elements while
predicatereturnstrueand returning the remaining elements.func dropFirst(Int) -> Self.SubSequence Returns a subsequence containing all but the given number of initial elements.
func dropLast(Int) -> Self.SubSequence 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: (Self.Element, OtherSequence.Element) throws -> Bool) rethrows -> 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<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) rethrows Calls the given closure on each element in the sequence in the same order as a
for-inloop.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) -> Bool Offsets the given index by the specified distance, or so that it equals the given limiting index.
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) -> 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: (Self.Element, Self.Element) throws -> Bool) rethrows -> 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>((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 prefix(Int) -> Self.SubSequence Returns a subsequence, up to the specified maximum length, containing the initial elements of the collection.
func prefix(through: Self.Index) -> Self.SubSequence Returns a subsequence from the start of the collection through the specified position.
func prefix(upTo: Self.Index) -> Self.SubSequence Returns 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.SubSequence Returns a subsequence containing the initial elements until
predicatereturnsfalseand 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 -> Result Returns the result of combining the elements of the sequence using the given closure.
func reduce<Result>(into: Result, (inout Result, Self.Element) throws -> ()) rethrows -> Result Returns the result of combining the elements of the sequence using the given closure.
func reversed() -> ReversedCollection<Self> Returns a view presenting the elements of the collection in reverse order.
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 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 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: (Self.Element, PossiblePrefix.Element) throws -> Bool) rethrows -> 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) -> Self.SubSequence Returns a subsequence, up to the given maximum length, containing the final elements of the collection.
func suffix(from: Self.Index) -> Self.SubSequence Returns a subsequence from the specified position to the end of the collection.
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.