指向 std::vector 对象的指针

Question

I need to do the following:

 std::vector<std::string> A; 
 std::vector<std::string> B;
 
 ==> pointer_to_vector<std::string> ptr;

//Some Code
ptr = A; //ptr points to object A

//Some More Code
ptr = B; // //ptr points to object B

During the program, ptr needs to refer to both A and B at different times. How would it be implemented and considering that std::vector makes reallocations, how to use smart pointers here?

Answer 1

You define a pointer to a vector the same way you define a pointer to any other type - using * in the pointer declaration, and the & address-of operator to get the memory address of a variable to assign to the pointer, eg:

std::vector<std::string> A; 
std::vector<std::string> B;
 
std::vector<std::string> *ptr;

//Some Code
ptr = &A; //ptr points to object A

//Some More Code
ptr = &B; // //ptr points to object B

Or, use std::addressof() , if any objects overload operator& for their own purposes (which std::vector does not), eg:

//Some Code
ptr = std::addressof(A); //ptr points to object A

//Some More Code
ptr = std::addressof(B); // //ptr points to object B