DiscoverUserIdentity.swift

CKContainer.default().requestApplicationPermission(.userDiscoverability) { status, error in
    guard status == .granted, error == nil else {
        // error handling voodoo
        return
    }

    CKContainer.default().discoverUserIdentity(withUserRecordID: recordID) { identity, error in
        guard let components = identity?.nameComponents, error == nil else {
            // more error handling magic
            return
        }

        DispatchQueue.main.async {
            let fullName = PersonNameComponentsFormatter().string(from: components)
            print("The user's full name is \(fullName)")
        }
    }
}