I have written my own operator<< implementation in my Logger class:

class Logger
{
public:

    enum Severity
    {
        INFORMATION = 0,
        WARNING = 1,
        ERROR = 2
    };

    Logger( std::ostream &os, Logger::Severity severity )
    : outputStream( os ), loggerSeverity( severity ) {}

    const std::vector<std::string>& getLogLines() const { return logLines; }

    friend Logger& operator<<( Logger &logger, Logger::Severity severity ) {
        logger.currentSeverity = severity;
        return logger;
    }

    friend Logger& operator<<( Logger &logger, const char *logLine ) {
        if( logger.currentSeverity >= logger.loggerSeverity )
        {
            logger.logLines.push_back( logLine );
            logger.outputStream << logLine;
        }
        return logger;
    }

private:
    std::ostream &outputStream;
    Logger::Severity loggerSeverity;
    std::vector<std::string> logLines;
    Logger::Severity currentSeverity;
    const std::map<Logger::Severity, std::string> severityMap =
    {
        { Logger::Severity::INFORMATION, "<INF>" },
        { Logger::Severity::WARNING, "<WARN>" },
        { Logger::Severity::ERROR, "<ERR>" }
    };
};

now I am wondering how I can supoprt std::hex formatting? I would like to be able to call my logger like this:

logger << Logger::Severity::ERROR << "CRC mismatch ( expected 0x" << std::hex << record->metaData.crc << " but got 0x" << std::hex << crc32 << std::dec << " )" << "n";

but I get:

error: no match for ‘operator<<’ (operand types are ‘Logger’ and ‘std::ios_base&(std::ios_base&)’)
   79 |         logger << Logger::Severity::ERROR << "CRC mismatch ( expected 0x" << std::hex << record->metaData.crc << " but got 0x" << std::hex << crc32 << std::dec << " )" << "n";
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^~ ~~~~~~~~
      |                                           |                                       |
      |                                           Logger                                  std::ios_base&(std::ios_base&)