Thread: "return function" doesn't work

here's my simplified codes:

Code:

class Drug
{
           public:
                   Drug(): avai(0) {};
                   bool& get_avai()
                   {
                            return avai;
                   }
           protected:
                   bool avai;
};

if (somedrug.get_avai()) 
{
            //do something
}

my compiler (Dev-C++) says " cannot convert Drug::get_avai()' to `

how come?