派生类的构造函数

#include <iostream>
using namespace std;

class Base{
public:
	Base(){
		cout << "This is Base constructor" << endl;
	}
	~Base(){
		cout << "THis is Base discontructor" << endl;
	}
	Base(int n): num(n){}

	void print(){
		cout << "Hello Base class: " << num << endl;
	}

private:
	int num = 1;
};

class Derived : public Base{
public:
	Derived(){
		cout << "This is Derived constructor" << endl;
	}
	~Derived(){
		cout << "THis is Derived disconstructor" << endl;
	}
	//基类如果有带参构造函数，那么派生类通过基类的构造函数
	//来初始化它的基类部分
	//首先初始化基类部分，然后再依次初始化它自己的部分
	Derived(int n): Base(n), code(n){}

	void greet(){
		cout << "Hello, Derived class: " << code << endl;
	}

private:
	int code = 2;
};

int main(){
	Derived A, B(10);
	A.print();
	A.greet();
	B.print();
	B.greet();
	return 0;
}