# withUnsafePointer(to:_:) Invokes the given closure with a pointer to the given argument. ``` func withUnsafePointer(to value: borrowing T, _ body: (UnsafePointer) throws(E) -> Result) throws(E) -> Result where E : Error, T : ~Copyable, Result : ~Copyable ``` ## Parameters `value` An instance to temporarily use via pointer. `body` A closure that takes a pointer to `value` as its sole argument. If the closure has a return value, that value is also used as the return value of the `withUnsafePointer(to:_:)` function. The pointer argument is valid only for the duration of the function’s execution. It is undefined behavior to try to mutate through the pointer argument by converting it to `UnsafeMutablePointer` or any other mutable pointer type. If you need to mutate the argument through the pointer, use `withUnsafeMutablePointer(to:_:)` instead. ## Return Value The return value, if any, of the `body` closure. ## Discussion The `withUnsafePointer(to:_:)` function is useful for calling Objective-C APIs that take in parameters by const pointer. The pointer argument to `body` is valid only during the execution of `withUnsafePointer(to:_:)`. Do not store or return the pointer for later use. --- 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)