# index(in:options:passingTest:) Returns the index of the first object in the specified range that passes the predicate Block test. ``` func index(in range: NSRange, options opts: NSEnumerationOptions = [], passingTest predicate: (Int, UnsafeMutablePointer) -> Bool) -> Int ``` ## Parameters `range` The range of indexes to test. `opts` A bitmask that specifies the options for the enumeration (whether it should be performed concurrently and whether it should be performed in reverse order). See [`NSEnumerationOptions`](/documentation/Foundation/NSEnumerationOptions) for the supported values. `predicate` The Block to apply to elements in the set. The Block takes two arguments: - idx: The index of the object. - stop: A reference to a Boolean value. The block can set the value to to stop further processing of the set. The `stop` argument is an out-only argument. You should only ever set this Boolean to YES within the Block. The Block returns a Boolean value that indicates whether `obj` passed the test. ## Return Value The index of the first object that passes the predicate test. ## Discussion --- 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)