# moveInitialize(fromContentsOf:) Moves every element of an initialized source buffer slice into the uninitialized memory referenced by this buffer slice, leaving the source memory uninitialized and this buffer slice’s memory initialized. ``` func moveInitialize(fromContentsOf source: Slice>) -> Slice.Index where Base == UnsafeMutableBufferPointer ``` ## Parameters `source` A buffer slice containing the values to copy. The memory region underlying `source` must be initialized. ## Return Value The index one past the last element of the buffer slice initialized by this function. ## Discussion Prior to calling the `moveInitialize(fromContentsOf:)` method on a buffer slice, the memory it references must be uninitialized, or its `Element` type must be a trivial type. After the call, the memory referenced by the buffer slice up to, but not including, the returned index is initialized. The memory referenced by `source` is uninitialized after the function returns. The buffer slice must reference enough memory to accommodate `source.count` elements. The returned index is the position of the next uninitialized element in the buffer slice, one past the index of the last element written. If `source` contains no elements, the returned index is equal to the slice’s `startIndex`. If `source` contains as many elements as the slice can hold, the returned index is equal to the slice’s `endIndex`. > Note: The memory regions referenced by `source` and this buffer slice > may overlap. > Precondition: `self.count` >= `source.count` --- 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)