Accessing a function, defined in the encapsulating structure, in the nested template function

Inner structs are mostly like regular struct, you need a instance of LoggingClass to access its non static members.

Demo providing one:

template <typename... Ts> struct FAEWE_LOG_THREAD { FAEWE_LOG_THREAD(LoggingClass& c, [[maybe_unused]]const char * formatString, [[maybe_unused]]Ts &&... logArguments, const std::source_location & sourceLocation = std::source_location::current() ) { ////////////////////////////////////////////////////////////// // How to access <getInstrumentsId()> defined in LoggingClass? std::cout << sourceLocation.function_name() << ": InstrumentsId from LoggingClass:" << c.getInstrumentsId() << std::endl; ////////////////////////////////////////////////////////////// } FAEWE_LOG_THREAD([[maybe_unused]]LoggingClass& c, [[maybe_unused]]bool fallbackToServer, [[maybe_unused]]const char * formatString, [[maybe_unused]]Ts &&... logArguments, [[maybe_unused]]const std::source_location & sourceLocation = std::source_location::current() ) { } }; template <typename... Ts> FAEWE_LOG_THREAD(LoggingClass& c, const char *, Ts &&... ) -> FAEWE_LOG_THREAD<Ts...>; template <typename... Ts> FAEWE_LOG_THREAD(LoggingClass& c, bool, const char *, Ts &&... ) -> FAEWE_LOG_THREAD<Ts...>; // [..] auto Faewe::demo() -> void { FAEWE_LOG_THREAD(*this, "Pi=%.3f", 3.141 ); FAEWE_LOG_THREAD(*this, true, "Euler's=%.3f", 2.718 ); std::cout << "InstrumentsId in LoggingClass=" << this->getInstrumentsId() << std::endl; }

Demo