如何避免使用ifdef使代码更可测试

Question

I am creating a log file for logging information. It has a switch to turn it on or off.

#define LOG_FILE

#ifdef LOG_FILE
    #define LOG(MESSAGE1, MESSAGE2) log(MESSAGE1, MESSAGE2);
#else
    #define LOG(MESSAGE1, MESSAGE2)
#endif

Now I can control logging using LOG_FILE switch. I was wondering there are any other way achieve similar feature which is more testable?

Answer 1

You can use templates like this:

#include <string>
#include <iostream>

#define USE_LOGGING true

template<bool>
inline void log(const std::string& message, const std::string&  verbosity) {}

template<>
inline void log<true>(const std::string& message, const std::string& verbosity) {
    std::cout << verbosity << ": " << message << "\n";
}

constexpr auto logMessage = log<USE_LOGGING>;

int main(int argc, char** argv) {
    logMessage("Test", "Warning");
}

By this you will have both versions available, using logMessage gives you the global settings, alternatively you can use log directly which is a local definition of how to use logging.