# init(capacity:) Returns an initialized mutable set with a given initial capacity. ``` init(capacity numItems: Int) ``` ## Parameters `numItems` The initial capacity of the set. ## Return Value An initialized mutable set with initial capacity to hold `numItems` members. The returned set might be different than the original receiver. ## Discussion Mutable sets allocate additional memory as needed, so `numItems` simply establishes the object’s initial capacity. This method is a designated initializer for `NSMutableSet`. ## See Also [`+ setWithCapacity:`](/documentation/Foundation/NSMutableSet/setWithCapacity:) Creates and returns a mutable set with a given initial capacity. --- 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)