What is good practice for generating verbose output?

Question

what is good practice for generating verbose output? currently, i have a function

bool verbose;
int setVerbose(bool v)
{
    errormsg = \"\";
    verbose = v;
           


        

Answer 1

The simplest way is to create small class as follows(here is Unicode version, but you can easily change it to single-byte version):

#include 
#include 
#include 
using namespace std;

enum log_level_t {
    LOG_NOTHING,
    LOG_CRITICAL,
    LOG_ERROR,
    LOG_WARNING,
    LOG_INFO,
    LOG_DEBUG
};

namespace log_impl {
class formatted_log_t {
public:
    formatted_log_t( log_level_t level, const wchar_t* msg ) : fmt(msg), level(level) {}
    ~formatted_log_t() {
        // GLOBAL_LEVEL is a global variable and could be changed at runtime
        // Any customization could be here
        if ( level <= GLOBAL_LEVEL ) wcout << level << L" " << fmt << endl;
    }        
    template  
    formatted_log_t& operator %(T value) {
        fmt % value;
        return *this;
    }    
protected:
    log_level_t     level;
    boost::wformat      fmt;
};
}//namespace log_impl
// Helper function. Class formatted_log_t will not be used directly.
template 
log_impl::formatted_log_t log(const wchar_t* msg) {
    return log_impl::formatted_log_t( level, msg );
}

Helper function log was made template to get nice call syntax. Then it could be used in the following way:

int main ()
{
    // Log level is clearly separated from the log message
    log(L"TEST %3% %2% %1%") % 5 % 10 % L"privet";
    return 0;
}

You could change verbosity level at runtime by changing global GLOBAL_LEVEL variable.