从基类实例调用派生类方法而不进行强制转换

Question

还有另一种方法可以在不强制转换的情况下从基指针对象调用派生类方法吗？

class Base
{
};

class Derived : public Base
{
    public:
    void set() {printf("bbbbbbbbbbbb"); }

};

int main()
{
  Base* pbBase;

  pbBase = new Derived();

  //pbBase->set(); // Compilation error.
  (Derived*)pbBase->set(); // Working.
}

Answer 1

您可以添加virtual的方法Base，你覆盖Derived。

请注意，您也应该创建析构函数virtual，否则当您delete通过基类指针创建对象时，不会调用派生类的析构函数。

#include <iostream>

class Base
{
public:
    virtual ~Base() = default;
    virtual void set() = 0;    // = 0 makes it pure virtual
};

class Derived : public Base
{
public:
    void set() override { std::cout << "bbbbbbbbbbbb\n"; }

};

int main()
{
  Base* pbBase;

  pbBase = new Derived();

  pbBase->set();

  delete pbBase;
}