---
title: MTLIOCommandBufferHandler
framework: metal
role: symbol
role_heading: Type Alias
path: metal/mtliocommandbufferhandler
---

# MTLIOCommandBufferHandler

A convenience type that defines the signature of an input/output command buffer’s completion handler.

## Declaration

```swift
typealias MTLIOCommandBufferHandler = @Sendable (any MTLIOCommandBuffer) -> Void
```

## Parameters

- `inputOutputCommandBuffer`: The doc://com.apple.metal/documentation/Metal/MTLIOCommandBuffer instance that has finished executing is calling your completion handler.

## See Also

### I/O command buffers

- [MTLIOCommandBuffer](metal/mtliocommandbuffer.md)
- [MTLIOFileHandle](metal/mtliofilehandle.md)
- [MTLIOStatus](metal/mtliostatus.md)
- [MTLIOError.Code](metal/mtlioerror-swift.struct/code.md)
- [MTLIOErrorDomain](metal/mtlioerrordomain.md)