How to initialize "ostream &out" in constructor, using "char *filename"

Question

Please help me in initializing "out" in the constructor?

class logger {
        ostream &out;

        public:
        logger(char *str) : out(/*How do i construct an object using str*/) {}    

        template <typename T> void print(T &obj) { out << obj; }
};

This class will be defined globally for others to just call the print method

UPDATE: I am planning to have below setup, where user of class can 1) create a new ostream object if he does not have one. He can create but he have to manage it as well. So do not want to give the feature. 2) If he have already have one he can pass on like "cout/cerr". 3) If he passes nothing "cerr" will be assumed.

{

    ostream &out;

    public:
    logger() : out(cerr) {}         
    logger(ostream &o) : out(o){}
    logger(char *str) : out(/*How do i construct an object using str*/) {}

}

Answer 1

There is no need for you to declare the stream as a reference, unless you want to be able to initialize from another stream. Something like this maybe:

class logger
{
    ofstream file;
    ostream &out;

public:
    logger(char *str) : file(str), out(file) {}
    logger(ostream &os) : out(os) {}

    // Other functions here, only using "out"
};