---
title: retain
framework: corefoundation
role: symbol
role_heading: Instance Property
path: corefoundation/cfarraycallbacks/retain
---

# retain

The callback used to retain each value as they are added to the collection. If NULL, values are not retained. See CFArrayRetainCallBack for a description of this callback.

## Declaration

```swift
var retain: CFArrayRetainCallBack!
```