---
title: "withUnsafePointer(to:_:)"
framework: swift
role: symbol
role_heading: Function
path: "swift/withunsafepointer(to:_:)-35wrn"
---

# withUnsafePointer(to:_:)

Invokes the given closure with a pointer to the given argument.

## Declaration

```swift
func withUnsafePointer<T, E, Result>(to value: borrowing T, _ body: (UnsafePointer<T>) 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

Return Value The return value, if any, of the body closure.

## Discussion

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.

## See Also

### Pointers to Values

- [withUnsafePointer(to:_:)](swift/withunsafepointer(to:_:)-9fjn6.md)
- [withUnsafeMutablePointer(to:_:)](swift/withunsafemutablepointer(to:_:).md)
- [withUnsafeBytes(of:_:)](swift/withunsafebytes(of:_:)-5zxtl.md)
- [withUnsafeBytes(of:_:)](swift/withunsafebytes(of:_:)-5gesg.md)
- [withUnsafeMutableBytes(of:_:)](swift/withunsafemutablebytes(of:_:).md)