c++ - 派生类C++访问派生类的基类

Question

whoAmI() 函数应该返回:

I am a Man
I am a Omnivore

但它只返回 "I am a Man" 两次:

class Animal
{
public:
  string className;
};

class Omnivore:public Animal
{
 public:
    Omnivore()
    {
        className = "Omnivore";
    }
};

class Man:public Omnivore
{
public:
    Man() {
        className = "Man";
    }
     void whoAmI()
     {
         cout << "I am a " << Omnivore::className << endl;
         cout << "I am a " << Omnivore::Animal::className << endl;
     }
};

Answer 1

只有一个Animal::className，它被Animal的构造函数初始化为空的std::string，然后赋值给"Omnivore" 由Omnivore 的构造函数赋值给Man，然后由Man 的构造函数赋值给Man。所以你得到了相同的结果，因为它们引用了相同的数据成员。

你可以让他们有自己的同名数据成员；但请注意，这不是一个好主意，派生类中的名称将隐藏基类中的名称。例如

class Animal
{
public:
  string className;
};

class Omnivore:public Animal
{
 public:
    string className;
    Omnivore()
    {
        className = "Omnivore";
    }
};

class Man:public Omnivore
{
public:
    string className;
    Man() {
        className = "Man";
    }
     void whoAmI()
     {
         cout << "I am a " << Omnivore::className << endl;         // "Omnivore"
         cout << "I am a " << Omnivore::Animal::className << endl; // empty
         cout << "I am a " << className << endl;                   // "Man"
     }
};