C++ 继承构造函数并扩展其功能

Question

我有一个基类，我想从中继承它的构造函数，但我想在子类中为构造函数添加更多内容。具体来说，我想在构造函数的末尾运行一个函数，比如 ExtraSetup()，它会执行一些与子类相关的初始化。有什么好的方法可以做到这一点？

这是一个简化的示例。我希望子类的 ExtraSetup() 在初始化子类对象时运行。请注意，我不一定要使用此“使用 Base::Base;”和虚函数。如果有更简单的方法就更好了。

#include <iostream>

using namespace std;


class Base {
    protected:
        int base_number_;
        
        virtual void ExtraSetup(){
            cout << "This should NOT run" << endl;
        }
        
    public:
        Base(int number){
            base_number_ = number;
            ExtraSetup();  
        }
};


class Sub : public Base {
    public:
        using Base::Base;
    private:
        int sub_number_;
        
        void ExtraSetup(){
            sub_number_ = 200;  // some random extra setup
            cout << "This should run" << endl;
        }
};


int main()
{
    Sub sub_object(100);
    return 0;
}

Answer 1

你也可以从你的“成员”部分继承：

class Base {
public:
    // Several constructors
    // We don't want to duplicate those in Derived class
    Base(int number);
    Base(int, int);
    Base(std::string);
};

class Member
{
protected:

    Member()
    {
       // some random extra setup
       std::cout << "This should run" << std::endl;
    }
};

class Derived : public Base, protected Member
{
public:
    int sub_number_ = 200; // If this kind of initialization is sufficient
                           // You might simply use it instead of inheritance
public:
    using Base::Base;
};