# indexOfObject(passingTest:) Returns the index of the first object in the array that passes a test in a given block. ``` func indexOfObject(passingTest predicate: (Any, Int, UnsafeMutablePointer) -> Bool) -> Int ``` ## Parameters `predicate` The block to apply to elements in the array. The block takes three arguments: - obj: The element in the array. - idx: The index of the element in the array. - stop: A reference to a Boolean value. The block can set the value to to stop further enumeration of the array. If a block stops further enumeration, that block continues to run until it’s finished. The `stop` argument is an out-only argument. You should only ever set this Boolean to within the block. The block returns a Boolean value that indicates whether `obj` passed the test. Returning will stop further processing of the array. ## Return Value The lowest index whose corresponding value in the array passes the test specified by `predicate`. If no objects in the array pass the test, returns `NSNotFound`. ## Discussion If the block parameter is `nil` this method will raise an exception. --- 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)