---
title: "CFErrorCopyFailureReason(_:)"
framework: corefoundation
role: symbol
role_heading: Function
path: "corefoundation/cferrorcopyfailurereason(_:)"
---

# CFErrorCopyFailureReason(_:)

Returns a human-presentable failure reason for a given error.

## Declaration

```swift
func CFErrorCopyFailureReason(_ err: CFError!) -> CFString!
```

## Parameters

- `err`: The CFError to examine. If this is not a valid CFError, the behavior is undefined.

## Return Value

Return Value A localized, human-presentable failure reason for err, or NULL if no user-presentable string is available. Ownership follows the The Create Rule.

## Discussion

Discussion The failure reason is a complete sentence which describes why the operation failed. In many cases this will be just the “because” part of the description (but as a complete sentence, which makes localization easier). For example, an error description “Could not save file ‘Letter’ in folder ‘Documents’ because the volume ‘MyDisk’ doesn’t have enough space.” might have a corresponding failure reason, “The volume ‘MyDisk’ doesn’t have enough space.” By default, this function looks for a value for the kCFErrorLocalizedFailureReasonKey key in the user info dictionary. Toll-free bridged instances of NSError might provide additional behaviors for manufacturing this value. When you create a CFError, you should try to make sure the return value is human-presentable and localized by providing a value for kCFErrorLocalizedFailureReasonKey in the user info dictionary.

## See Also

### Getting Information About an Error

- [CFErrorGetDomain(_:)](corefoundation/cferrorgetdomain(_:).md)
- [CFErrorGetCode(_:)](corefoundation/cferrorgetcode(_:).md)
- [CFErrorCopyUserInfo(_:)](corefoundation/cferrorcopyuserinfo(_:).md)
- [CFErrorCopyDescription(_:)](corefoundation/cferrorcopydescription(_:).md)
- [CFErrorCopyRecoverySuggestion(_:)](corefoundation/cferrorcopyrecoverysuggestion(_:).md)