Which way do you recommend to check whether CloudKit is reachable but before any operation would start on it?
execute the requestApplicationPermission on the container.
see the documentation at: xcdoc://?url=developer.apple.com/library/prerelease/ios/documentation/CloudKit/Reference/CKContainer_class/index.html
For a working sample you can have a look at: https://github.com/evermeer/EVCloudKitDao