Before I used JSON-framework,https://github.com/stig/json-framework/, it was great. But now I get an error "Unknow property attribute". Even when I run the example provided with the framework I have the same error

Before I used JSON-framework,https://github.com/stig/json-framework/, it was great. But now I get an error "Unknow property attribute". Even when I run the example provided with the framework I have the same error

Copyright © 2021 Jogjafile Inc.
Upgrade your Xcode to version 4.2 to get the quoted source code compiled successfully.