---
title: SecMessageBlock
framework: security
role: symbol
role_heading: Type Alias
path: security/secmessageblock
---

# SecMessageBlock

A block that delivers messages during asynchronous operations.

## Declaration

```swift
typealias SecMessageBlock = (CFTypeRef?, CFError?, Bool) -> Void
```

## Parameters

- `message`: A CFType containing the message. This is where either intermediate or final results are returned.
- `error`: If an error occurred, this will contain a CFErrorRef, otherwise this will be NULL. If not NULL the caller is responsible for releasing the CFErrorRef.
- `isFinal`: If set the message returned is the final result otherwise it is an intermediate result.