# enumerateObjects(at:options:using:) Executes a given block using the objects in the array at the specified indexes. ``` func enumerateObjects(at s: IndexSet, options opts: NSEnumerationOptions = [], using block: (Any, Int, UnsafeMutablePointer) -> Void) ``` ## Parameters `s` The indexes of the objects over which to enumerate. `opts` A bit mask that specifies the options for the enumeration (whether it should be performed concurrently and whether it should be performed in reverse order). `block` 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. When the `NSEnumerationConcurrent` enumeration option is specified, enumeration stops after all of the currently running blocks finish. The `stop` argument is an out-only argument. You should only ever set this Boolean to within the block. ## Discussion By default, the enumeration starts with the first object and continues serially through the array to the last element specified by `indexSet`. You can specify `NSEnumerationConcurrent` and/or `NSEnumerationReverse` as enumeration options to modify this behavior. This method executes synchronously. > Important: > If the block parameter or the `indexSet` is `nil` this method will raise an exception. ## See Also [`makeObjectsPerformSelector:`](/documentation/Foundation/NSArray/makeObjectsPerformSelector:) Sends to each object in the array the message identified by a given selector, starting with the first object and continuing through the array to the last object. [`makeObjectsPerformSelector:withObject:`](/documentation/Foundation/NSArray/makeObjectsPerformSelector:withObject:) Sends the `aSelector` message to each object in the array, starting with the first object and continuing through the array to the last object. --- 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)