# 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(_ i: Int, offsetBy n: Int, limitedBy limit: Int) -> Int? ``` ## Parameters `i` A valid index of the collection. `limit` A valid index of the collection to use as a limit. If `distance > 0`, a limit that is less than `i` has no effect. Likewise, if `distance < 0`, a limit that is greater than `i` has no effect. ## Return Value An index offset by `distance` from the index `i`, unless that index would be beyond `limit` in the direction of movement. In that case, the method returns `nil`. ## Discussion The following example obtains an index advanced four positions from a string’s starting index and then prints the character at that position. The operation doesn’t require going beyond the limiting `s.endIndex` value, so it succeeds. ``` let s = "Swift" if let i = s.index(s.startIndex, offsetBy: 4, limitedBy: s.endIndex) { print(s[i]) } // Prints "t" ``` The next example attempts to retrieve an index six positions from `s.startIndex` but fails, because that distance is beyond the index passed as `limit`. ``` let j = s.index(s.startIndex, offsetBy: 6, limitedBy: s.endIndex) print(j) // Prints "nil" ``` The value passed as `distance` must not offset `i` beyond the bounds of the collection, unless the index passed as `limit` prevents offsetting beyond those bounds. > Complexity: O(1) if the collection conforms to > `RandomAccessCollection`; otherwise, O(*k*), where *k* is the absolute > value of `distance`. --- 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)