c++ - 从基类调用重写的方法

Question

在以下场景中如何从基类调用重写的 bar 方法？

要求回调应始终调用方法 foo，该方法应调用由最新派生类覆盖的 bar。

#include <iostream>
#include <functional>
#include <typeinfo>

using namespace std;

std::function<void(void)> callback = nullptr;

class Base {
 public:
  Base(Base* ptr) { callback = std::bind(&Base::foo, *ptr); }

  virtual ~Base() {}

  virtual void foo() {
    bar();  // How call foo() from Derived instead of Base?
  }
  virtual void bar() { cout << "Base::bar" << endl; }
};

class Derived : public Base {
 public:
  Derived() : Base(this) {}

  virtual void bar() override { cout << "Derived::bar" << endl; }
};

int main() {
  cout << "Hello World" << endl;
  Base* b = new Derived();

  cout << "**callback**" << endl;
  callback();  // output should be 'Derived::bar'

  return 0;
}

Answer 1

您将虚拟方法与派生对象绑定(bind)不当，从而对派生对象进行了切片。试试这个(* 已删除)

Base(Base *ptr){
    callback = std::bind(&Base::foo, ptr);
}