Const Member Function Pointers

1class MyClass {
2 public:
3  int getValue() const { return value; }
4
5 private:
6  int value = 42;
7};
8
9// Pointer to const member function
10int (MyClass::*constMemberPtr)() const =
11  &MyClass::getValue;

1auto getter = std::mem_fn(&MyClass::getValue);
2const MyClass obj;
3std::cout << getter(obj);  // Outputs: 42

1std::function<int(const MyClass&)> func =
2  &MyClass::getValue;

1#include <iostream>
2
3class Rectangle {
4 public:
5  int getArea() const { return width * height; }
6  int width = 5, height = 3;
7};
8
9int main() {
10  int (Rectangle::*areaPtr)() const =
11    &Rectangle::getArea;
12
13  const Rectangle r;
14  std::cout << (r.*areaPtr)() << '\n';
15
16  const Rectangle* pr = &r;
17  std::cout << (pr->*areaPtr)();
18}

1template <typename Class, typename Func>
2auto callMember(
3  const Class& obj, Func Class::*memberFunc
4) {
5  return (obj.*memberFunc)();
6}
7
8int main() {
9  const Rectangle r;
10
11  // Outputs: 15
12  std::cout << callMember(r, &Rectangle::getArea);
13}

1#include <iostream>
2
3class OverloadedClass {
4 public:
5  int getValue() { return 1; }
6  int getValue() const { return 2; }
7};
8
9int main() {
10  int (OverloadedClass::*nonConstPtr)() =
11    &OverloadedClass::getValue;
12  int (OverloadedClass::*constPtr)() const =
13    &OverloadedClass::getValue;
14
15  OverloadedClass obj;
16  const OverloadedClass constObj;
17
18  std::cout << (obj.*nonConstPtr)() << '\n';
19  std::cout << (constObj.*constPtr)();
20}