Suppressing “'…' is deprecated” when using respondsToSelector

Question

I\'m supporting 10.4+ by picking the most-current API at runtime:

if ([fileManager respondsToSelector:@selector(removeItemAtPath:error:)])
    [fileManager r         


        

Answer 1

If you consider any form of "confusing" the compiler to be an invalid solution, you're probably going to have to live with the warning. (In my book, if you asking how to get rid of a warning, it's unwise to look a gift horse in the mouth and say something is invalid just because it doesn't look like you'd expect.)

The answers that work at runtime involve masking the operation that's happening with dynamic dispatch so the compiler doesn't complain about the deprecated call. If you don't like that approach, you can turn off "Warn About Deprecated Functions" in your Xcode project or target settings, but that's generally a bad idea. You want to know about deprecated APIs, but in this case you want to use it without warning. There are easy and hard ways to do this, and odds are you'd consider all of them "invalid" in some form, but that doesn't prevent them from being effective, even correct. ;-)

One possible way to avoid the warnings yet still select at runtime is to use objc_msgSend() directly:

objc_msgSend(fileManager, @selector(removeFileAtPath:error:), downloadDir, nil];

This is what the Objective-C runtime does under the covers anyway, and should accomplish the result you want with a minimum of fuss. You can even leave the original line commented above it for clarity. I know the documentation says, "The compiler generates calls to the messaging function. You should never call it directly in the code you write." You alone have to decide when it's okay to bend the rules.