using operator & after class method name [duplicate]

Question

I found the C++ class with API like this:

class foo
{
.....
public:
int& func1() & ;
int func1() && ;
.....
}

what does operator & and && do after the method name and what is the difference between these two function.

Vittorio Romeo · Accepted Answer · 2018-08-03 09:36:50Z

3

These are called "ref qualifiers" and allow you to overload a member function depending on the value category of *this.

int& func1() & means: this overload of func1 can be invoked on any instance of *this which can be bound to an lvalue reference.
int func1() && means: this overload of func1 can be invoked on any instance of *this which can be bound to an rvalue reference.

E.g.

foo f; f.func1(); // calls &-qualified version
foo{}.func1();    // calls &&-qualified version

answered Aug 3, 2018 at 9:36

Vittorio Romeo

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