---
title: CFComparatorFunction
framework: corefoundation
role: symbol
role_heading: Type Alias
path: corefoundation/cfcomparatorfunction
---

# CFComparatorFunction

Callback function that compares two values. You provide a pointer to this callback in certain Core Foundation sorting functions.

## Declaration

```swift
typealias CFComparatorFunction = (UnsafeRawPointer?, UnsafeRawPointer?, UnsafeMutableRawPointer?) -> CFComparisonResult
```

## Parameters

- `val1`: The first value to compare.
- `val2`: The second value to compare.
- `context`: An untyped pointer to the context of the evaluation. The meaning of this value and its use are defined by each comparator function. This value is usually passed to a sort function, such as doc://com.apple.corefoundation/documentation/CoreFoundation/CFArraySortValues(_:_:_:_:), which then passes it, unchanged, to the comparator function.

## Return Value

Return Value A CFComparisonResult value that indicates whether the val1 is equal to, less than, or greater than val2. See CFComparisonResult for a list of possible values.

## Discussion

Discussion If you need to sort the elements in a collection using special criteria, you can implement a comparator function with the signature defined by this prototype. You pass a pointer to this function in one of the “sort” functions, such as CFArray’s CFArraySortValues(_:_:_:_:). You can also pass pointers to standard Core Foundation comparator functions such as CFStringCompare(_:_:_:) and CFDateCompare(_:_:_:).