Passing variables by reference and construct new objects

Question

Hello there i have code like this one below and i don\'t know why it doesn\'t work.

class Clazz2;
class Clazz
{
    public:
    void smth(Clazz2& c)
    {

          


        

Answer 1

This is because non-constant references are not allowed to bind to temporary objects. References to const, on the other hand, can bind to temporary objects (see 8.3.5/5 of the C++11 Standard).

Answer 2

Your first smth2 takes a reference, which cannot be bound to a temporary like your constructor call a.smth(Claszz2()). However, a const reference can be bound to a temporary because we cannot modify the temporary, so it is allowed.

In C++11, you can use an rvalue-refrerence so that you have the ability to bind temporaries as well:

void smth2(Clazz2 &&);

int main()
{
    a.smth(Claszz2()); // calls the rvalue overload
}