---
title: SecTransformInstanceBlock
framework: security
role: symbol
role_heading: Type Alias
path: security/sectransforminstanceblock
---

# SecTransformInstanceBlock

A block that you return from a transform creation function.

## Declaration

```swift
typealias SecTransformInstanceBlock = () -> Unmanaged<CFError>?
```

## Return Value

Return Value A an error object if an error occurred.

## Discussion

Discussion You return a block of this type from the custom transform creation function of type SecTransformCreateFP that you register with the SecTransformRegister(_:_:_:) function.