# BidirectionalCollection Implementations ## Topics ### Instance Properties [`var endIndex: String.UnicodeScalarView.Index`](/documentation/Swift/String/UnicodeScalarView/endIndex) The “past the end” position—that is, the position one greater than the last valid subscript argument. [`var last: Self.Element?`](/documentation/Swift/String/UnicodeScalarView/last) The last element of the collection. [`var startIndex: String.UnicodeScalarView.Index`](/documentation/Swift/String/UnicodeScalarView/startIndex) The position of the first Unicode scalar value if the string is nonempty. ### Instance Methods [`func difference(from: C) -> CollectionDifference`](/documentation/Swift/String/UnicodeScalarView/difference(from:)) Returns the difference needed to produce this collection’s ordered elements from the given collection. [`func difference(from: C, by: (C.Element, Self.Element) -> Bool) -> CollectionDifference`](/documentation/Swift/String/UnicodeScalarView/difference(from:by:)) Returns the difference needed to produce this collection’s ordered elements from the given collection, using the given predicate as an equivalence test. [`func distance(from: String.UnicodeScalarView.Index, to: String.UnicodeScalarView.Index) -> Int`](/documentation/Swift/String/UnicodeScalarView/distance(from:to:)) Returns the distance between two indices. [`func dropLast(Int) -> Self.SubSequence`](/documentation/Swift/String/UnicodeScalarView/dropLast(_:)) Returns a subsequence containing all but the specified number of final elements. [`func formIndex(before: inout Self.Index)`](/documentation/Swift/String/UnicodeScalarView/formIndex(before:)) Replaces the given index with its predecessor. [`func index(String.UnicodeScalarView.Index, offsetBy: Int) -> String.UnicodeScalarView.Index`](/documentation/Swift/String/UnicodeScalarView/index(_:offsetBy:)) Returns an index that is the specified distance from the given index. [`func index(String.UnicodeScalarView.Index, offsetBy: Int, limitedBy: String.UnicodeScalarView.Index) -> String.UnicodeScalarView.Index?`](/documentation/Swift/String/UnicodeScalarView/index(_:offsetBy:limitedBy:)) Returns an index that is the specified distance from the given index, unless that distance is beyond a given limiting index. [`func index(after: String.UnicodeScalarView.Index) -> String.UnicodeScalarView.Index`](/documentation/Swift/String/UnicodeScalarView/index(after:)) Returns the next consecutive location after `i`. [`func index(before: String.UnicodeScalarView.Index) -> String.UnicodeScalarView.Index`](/documentation/Swift/String/UnicodeScalarView/index(before:)) Returns the previous consecutive location before `i`. [`func last(where: (Self.Element) throws -> Bool) rethrows -> Self.Element?`](/documentation/Swift/String/UnicodeScalarView/last(where:)) Returns the last element of the sequence that satisfies the given predicate. [`func lastIndex(of: Self.Element) -> Self.Index?`](/documentation/Swift/String/UnicodeScalarView/lastIndex(of:)) Returns the last index where the specified value appears in the collection. [`func lastIndex(where: (Self.Element) throws -> Bool) rethrows -> Self.Index?`](/documentation/Swift/String/UnicodeScalarView/lastIndex(where:)) Returns the index of the last element in the collection that matches the given predicate. [`func reversed() -> ReversedCollection`](/documentation/Swift/String/UnicodeScalarView/reversed()) Returns a view presenting the elements of the collection in reverse order. [`func suffix(Int) -> Self.SubSequence`](/documentation/Swift/String/UnicodeScalarView/suffix(_:)) Returns a subsequence, up to the given maximum length, containing the final elements of the collection. ### Subscripts [`subscript(String.UnicodeScalarView.Index) -> Unicode.Scalar`](/documentation/Swift/String/UnicodeScalarView/subscript(_:)-2op53) Accesses the Unicode scalar value at the given position. [`subscript(Range) -> String.UnicodeScalarView.SubSequence`](/documentation/Swift/String/UnicodeScalarView/subscript(_:)-6aml8) Accesses a contiguous subrange of the collection’s elements. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)