How to create functions like std::cout?

Question

I\'m creating my own logging utility for my project, I want to create a function like iostream\'s std::cout, to log to a file and print to the console as well.

Here\

Answer 1

The trick is for your LOG(level) to return a special type which contains a pointer to an std::ostream, and defines the << operator. Something like:

class LogStream
{
    std::ostream* myDest;
public:
    LogStream( std::ostream* dest ) : myDest( dest ) {}

    template 
    LogStream& operator<<( T const& obj )
    {
        if ( myDest != nullptr ) {
            *myDest << obj;
        }
        return *this;
    }
};

The LOG(level) macro creats an instance of one, something like:

#define LOG(level) LogStream( getLogStream( level, __FILE__, __LINE__ ) )

Of course, the getLogStream may insert any information it wants (like a timestamp) at the moment it is called.

You might want to add a flush in the destructor of LogStream.