Pointer getter to a reference - c++

Question

I have a class with a reference and want a getter that returns a pointer.
class X {
std::string& text;
public:
auto GetText() -> decltype(text) * { return &text); // doesn't work
X(std::string& text): text(text) {}
};
The easy way is to pass a pointer to this class. But if I pass a reference, can I get a pointer with a getter?
Edit: here is the error message
error: cannot declare pointer to 'std::__cxx11::string& {aka class std::__cxx11::basic_string<char>&}'
auto GetText() -> decltype(text) * { return &text);
^

Answer 1

Firstly,
auto GetText() -> decltype(text) * { return &text); // doesn't work
is a positively abominable way to declare this signature. Prefer
std::string* GetText(){ return &text);
or even just
auto GetText(){ return &text);
But this isn't code review.
The problem here is that you're asking for a pointer to the declared type of the text member variable which is a string reference (std::string&). From the comment section, it seems you were unaware that decltype respects the 'reference'ness, 'const'ness, and 'volatile'ness of its argument.
You cannot have a pointer to a reference in C++, e.g. std::string&* is malformed. Calling to std::remove_reference_t should resolve that issue, e.g.
auto GetText() -> std::remove_reference_t<decltype(text)> * { return &text);
However, in this case, auto would have correctly deduced your type anyway, so your explicit declaration is unnecessary.

Answer 2

I've made a test program for my initial problem. The program has a class with a pointer and a getter that returns a reference and a second class with a reference and a getter that returns a pointer.
And it seems that -> std::remove_reference_t<decltype(text)> can be substituted with -> decltype(&text).
Feel free to comment.
// g++ main.cpp -o test_reference_pointer && strip -s test_reference_pointer && ./test_reference_pointer
#include <iostream>
// A class with a pointer and a getter that returns a reference.
class A {
std::string *text;
public:
std::string& GetText_old_way() { return *text; }
auto GetText_pure_auto() { return *text; }
auto GetText_pointer_arithmetic() -> decltype(*text) & { return *text; }
public:
A(std::string *text): text(text) {}
};
// A class with a reference and a getter that returns a pointer.
class B {
std::string& text;
public:
std::string *GetText_old_way() { return &text; }
auto GetText_pure_auto() { return &text; }
auto GetText_pointer_arithmetic() -> decltype(&text) { return &text; }
auto GetText_remove_reference() -> std::remove_reference_t<decltype(text)> * { return &text; }
public:
B(std::string& text): text(text) {}
};
int main() {
std::string text = "hello, world";
{//TEST
A a(&text);
unsigned int i{0};
std::cout << "-- Test 1:"<< std::endl;
++i; std::cout << i << ". " << a.GetText_old_way() << std::endl;
++i; std::cout << i << ". " << a.GetText_pointer_arithmetic() << std::endl;
++i; std::cout << i << ". " << a.GetText_pure_auto() << std::endl;
std::cout << std::endl;
}
{//TEST
B b(text);
unsigned int i{0};
std::cout << "-- Test 2:"<< std::endl;
++i; std::cout << i << ". " << *b.GetText_old_way() << std::endl;
++i; std::cout << i << ". " << *b.GetText_pointer_arithmetic() << std::endl;
++i; std::cout << i << ". " << *b.GetText_remove_reference() << std::endl;
++i; std::cout << i << ". " << *b.GetText_pure_auto() << std::endl;
std::cout << std::endl;
}
return 0;
}