# RandomAccessCollection Implementations ## Topics ### Instance Properties [`var endIndex: Int`](/documentation/Swift/ArraySlice/endIndex) The array’s “past the end” position—that is, the position one greater than the last valid subscript argument. [`var indices: Range`](/documentation/Swift/ArraySlice/indices-swift.property) The indices that are valid for subscripting the collection, in ascending order. [`var startIndex: Int`](/documentation/Swift/ArraySlice/startIndex) The position of the first element in a nonempty array. ### Instance Methods [`func distance(from: Int, to: Int) -> Int`](/documentation/Swift/ArraySlice/distance(from:to:)) Returns the distance between two indices. [`func formIndex(after: inout Int)`](/documentation/Swift/ArraySlice/formIndex(after:)) Replaces the given index with its successor. [`func formIndex(before: inout Int)`](/documentation/Swift/ArraySlice/formIndex(before:)) Replaces the given index with its predecessor. [`func index(Int, offsetBy: Int) -> Int`](/documentation/Swift/ArraySlice/index(_:offsetBy:)) Returns an index that is the specified distance from the given index. [`func index(Int, offsetBy: Int, limitedBy: Int) -> Int?`](/documentation/Swift/ArraySlice/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: Int) -> Int`](/documentation/Swift/ArraySlice/index(after:)) Returns the position immediately after the given index. [`func index(before: Int) -> Int`](/documentation/Swift/ArraySlice/index(before:)) Returns the position immediately before the given index. ### Subscripts [`subscript(Int) -> Element`](/documentation/Swift/ArraySlice/subscript(_:)-4e8d9) Accesses the element at the specified position. [`subscript(Range) -> ArraySlice`](/documentation/Swift/ArraySlice/subscript(_:)-63qca) Accesses a contiguous subrange of the array’s elements. ### Type Aliases [`typealias Index`](/documentation/Swift/ArraySlice/Index) The index type for arrays, `Int`. [`typealias Indices`](/documentation/Swift/ArraySlice/Indices) The type that represents the indices that are valid for subscripting an array, in ascending order. --- 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)