# CFShow(_:) Prints a description of a Core Foundation object to stderr. ``` func CFShow(_ obj: CFTypeRef!) ``` ## Parameters `obj` A Core Foundation object derived from CFType. If `obj` is not a Core Foundation object, an assertion is raised. ## Discussion The output is printed to the standard I/O standard error (stderr). This function is useful as a debugging aid for Core Foundation objects. Because these objects are based on opaque types, it is difficult to examine their contents directly. However, the opaque types implement `description` function callbacks that return descriptions of their objects. This function invokes these callbacks. ### Special Considerations You can use `CFShow` in one of two general ways. If your debugger supports function calls (such as `gdb` does), call `CFShow` in the debugger: ```objc (gdb) call (void) CFShow(string) Hello World ``` You can also incorporate calls to `CFShow` in a test version of your code to print out “snapshots” of Core Foundation objects to the console. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)