How to create an array with reference member in C++?

Question

I have some class Foo and Logger:

class Logger{/* something goes here */};
class Foo{
  Foo(Logger& logger);
  Logger& logger;
}

Foo::Foo(Logger& logger) : logger(logger)
{}

Now I want to create an array of objects of class Foo, where all references Foo::logger should point to the same Logger object. I tried something like (I need both stack and heap allocation):

Logger log (/* parameters */);
Foo objects [3] (log); // On stack
Foo* pObjects = new Foo [3] (log); // On heap

The problem is that both versions try to call the default constructor Foo() which is not present. Also as I understand it is not possible to change the referenced variable of a reference. So a temporary call to the default constructor and a later initalisation in a loop does also not help.

So: What is the right way to do it? Do I need to use pointers to the Logger object?

Answer 1

You cannot initialize an array of objects with non-default constructor. However you can use a vector as shown here (Look at the first reply)

And for the heap you can do the following :

Foo* pObjects[3];

for (int i = 0; i < 3; ++i) {
   pObjects[i] = new Foo(log);
}

Answer 2

For general uses I normally make a logger a Singleton so there is only one and can be accessed from all components. http://en.wikipedia.org/wiki/Singleton_pattern

This also makes the constructor of Foo much simpler.

class Logger
{
    public:
        static Logger& getInstance()
        {
            static Logger    instance;
            return instance;
        }

        public log(const std::string& txt) 
        {
            //do something
        }

    private:
        Logger() {}
        Logger(Logger const&);              // Don't Implement.
        void operator=(Logger const&); // Don't implement
 };

And use it in Foo like:

 Logger::getInstance().log("test");

or

 Logger& logger = Logger::getInstance();
 logger.log("test");

(Credits for singleton from @Loki Astari : C++ Singleton design pattern )