---
title: UniqueArray.Index
framework: Swift
role: symbol
role_heading: Type Alias
platforms: [iOS 27.0+, iPadOS 27.0+, Mac Catalyst 27.0+, macOS 27.0+, tvOS 27.0+, visionOS 27.0+, watchOS 27.0+]
path: swift/uniquearray/index
---

# UniqueArray.Index

A type that represents a position in the array: an integer offset from the start.

## Declaration

```swift
typealias Index = Int
```

## Discussion

Discussion Valid indices consist of the position of every element and a “past the end” position that’s not valid for use as a subscript argument.