c++ - 抽象基类或派生类中的类变量？

Question

我有一个抽象类，它有一个字符串变量 owner_。每个派生类都声明了这个变量的名称。将变量放在抽象基类中是更好的做法，还是我可以更好地在派生类中多次实现它？

#include <string>
#include <iostream>

class Pet
{
    public:
        Pet(const std::string& owner) : owner_(owner) {}
        virtual ~Pet() = 0;
        virtual void print_status() = 0;
    protected:
        const std::string owner_;
};

Pet::~Pet() {}

class Dog : public Pet
{
    public:
        Dog(const std::string& owner) : Pet(owner) {}
        ~Dog() {};
        void print_status()
        {
            std::string s = "Woof! My owner is ";
            s += owner_;
            std::cout << s << std::endl;
        }
    // Or better here?
    // private:
    //     const std::string owner_;
};

class Cat : public Pet
{
    public:
        Cat(const std::string& owner) : Pet(owner) {}
        ~Cat() {};
        void print_status()
        {
            std::string s = "Meow! My owner is ";
            s += owner_;
            std::cout << s << std::endl;
        }
    // Or better here?
    // private:
    //     const std::string owner_;
};

int main()
{
    Dog dog("Mario");
    dog.print_status();

    Cat cat("Luigi");
    cat.print_status();

    return 0;
}

Answer 1

IMO 这正是抽象基类的用途:为继承层次结构中的接口(interface)提供通用实现。
我只是更进一步，甚至将接口(interface)与抽象基类分开:

struct IPet {
    virtual ~IPet() = {}
    virtual void print_status() = 0;
    virtual const std::string& get_owner() const = 0;
};

class Pet : public IPet
{
public:
    Pet(const std::string& owner) : owner_(owner) {}
    virtual const std::string& get_owner() const { return owner_; }
    virtual ~Pet() {} // = 0; Don't declare the destructor as pure virtual function
    virtual void print_status() = 0;
protected:
    std::string owner_;
};