---
title: header
framework: Hypervisor
role: symbol
role_heading: Instance Property
path: hypervisor/hv_ion_message_t/header
---

# header

The Mach message header.

## Declaration

```swift
var header: mach_msg_header_t
```

## See Also

### Instance properties

- [addr](hypervisor/hv_ion_message_t/addr.md)
- [size](hypervisor/hv_ion_message_t/size.md)
- [trailer](hypervisor/hv_ion_message_t/trailer.md)
- [value](hypervisor/hv_ion_message_t/value.md)