Question

I have the following code:

void cStatisticDBSerializer::GetStats (std::map <std::string, long long >& ioCounterStats,
                                       std::map <std::string, long long >& ioGaugeStats,
                                       bool iSwitch)
{
   // Before getting the stats, clear the containers 
   ioCounterStats.clear ();
   ioGaugeStats.clear ();

   std::map <std::string, long long >& lStats = ioCounterStats;

   if (iSwitch)
   {
      lStats = ioGaugeStats;
   }

   // Do something with lStats
}

The question is: Is it valid to assign the function input reference to the local variable lStats? For some reason, this compiles fine, but does not behave as expected. However, if I change lStats to a pointer and assign it as follows (e.g.):

std::map <std::string, long long >* lpStats = &ioCounterStats;

It works just fine.

Could somebody please explain what’s going on here. Thanks!

Answer 1

You can’t reassign a reference once it has been created. Instead every use of it will “refer” to the original assignment. Your first example is equivalent to:

ioCounterStats /*lStats*/ = ioGaugeStats;