C ++ Access派生类成员从基类指针 [英] C++ Access derived class member from base class pointer

问题描述

class Base
{
    public:
    int base_int;
};

class Derived : public Base
{
    public:
    int derived_int
};

Base* basepointer = new Derived();
basepointer-> //Access derived_int here, is it possible? If so, then how?

推荐答案

不，您不能访问由于 derived_int 是 Derived 的一部分，而 basepointer 是指向 Base 的指针。

No, you cannot access derived_int because derived_int is part of Derived, while basepointer is a pointer to Base.

Derived* derivedpointer = new Derived;
derivedpointer->base_int; // You can access this just fine

派生类继承基类的成员，

Derived classes inherit the members of the base class, not the other way around.

但是，如果 basepointer 指向 Derived 然后你可以通过转换访问它：

However, if your basepointer was pointing to an instance of Derived then you could access it through a cast:

Base* basepointer = new Derived;
static_cast<Derived*>(basepointer)->derived_int; // Can now access, because we have a derived pointer

请注意，继承 public 第一个：

class Derived : public Base

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