"selector not recognized" - Including Static Libraries

If your Xcode project includes static libraries which further access category methods, you could run into the issue of "selector not recognized" for a custom category method.

The key is to add the -ObjC flag to "Other Linker Flags".

For more details, Apple has a nice Technical Note on this -

https://developer.apple.com/library/mac/qa/qa1490/_index.html