Constructor for '' must explicitly initialize the reference member ''

Question

I have this class

class CamFeed { public:     // constructor     CamFeed(ofVideoGrabber &cam);      ofVideoGrabber &cam;  }; 

And this constructor:

CamFeed::CamFeed(ofVideoGrabber &cam) {     this->cam = cam; } 

I get this error on the constructor: Constructor for '' must explicitly initialize the reference member ''

What is a good way to get around this?

Answer 1

You need to use the constructor initializer list:

CamFeed::CamFeed(ofVideoGrabber& cam) : cam(cam) {} 

This is because references must refer to something and therefore cannot be default constructed. Once you are in the constructor body, all your data members have been initialized. Your this->cam = cam; line would really be an assignment, assigning the value referred to by cam to whatever this->cam refers to.