---
title: preferredSize
framework: corefoundation
role: symbol
role_heading: Instance Property
path: corefoundation/cfallocatorcontext/preferredsize
---

# preferredSize

A prototype for a function callback that determines whether there is enough free memory to satisfy a request. In implementing this function, return the actual size the allocator is likely to allocate given a request for a block of memory of size size. The hint argument is a bitfield that you should currently not use.

## Declaration

```swift
var preferredSize: CFAllocatorPreferredSizeCallBack!
```