C++的继承中构造和析构函数的调用顺序

柔情只为你懂 2022-06-09 14:07 229阅读 0赞

实例：

#include <iostream>
    using namespace std;
    class parent{
    public:
    	parent(int a, int b, int d)
    	{
    		this->a = a;
    		this->b = b;
    		this->d = d;
    		cout << "基类构造" << endl;
    	}
    	~parent()
    	{
    		cout << "基类析构" << endl;
    	}
    public:
    	int a;
    private:
    	int b;
    protected:
    	int d;
    };
    class child3 : public parent
    {
    public:
    	child3(int c, int a, int b, int d) : parent(a, b, d)
    	{
    		this->c = c;
    		cout << "派生类构造函数" << endl;
    	}
    	~child3()
    	{
    		cout << "派生类析构函数" << endl;
    	}
    public:
    private:
    	int c;
    protected:
    };
    int main()
    {
    	{
    		child3 oop(1, 2, 3, 3);
    	}
    	system("pause");
    	return 0;
    }

在上述代码中，程序在执行时会先进入到基类的构造函数执行parent(int a,int b,int c)构造函数，当构造函数执行结束后打印基类构造函数，然后继续执行child3的构造函数child3(int c,int a,int b,int  d),当该构造函数执行结束后打印派生类构造函数，然后进入到派生类析构函数执行，执行完成最后执行基类析构函数，最后打印基类析构函数；

混搭情况下构造和析构函数的调用规则：

构造：先调用父类构造函数，在调用构造成员，最后调用自己的构造函数；

析构：先析构自己，在析构成员变量，最后析构父类

#include <iostream>
    using namespace std;
    class Grad{
    public:
    	Grad(int _a, int _b)
    	{
    		this->_a = _a;
    		this->_b = _b;
    		cout << "Grad 构造函数" << endl;
    	}
    	~Grad()
    	{
    		cout << "Grad析构函数" << endl;
    	}
    private:
    	int _a;
    	int _b;
    };
    class parent 
    {
    public:
    	parent(int a, int b, int d) 
    	{
    		this->a = a;
    		this->b = b;
    		this->d = d;
    		cout << "基类构造" << endl;
    	}
    	~parent()
    	{
    		cout << "基类析构" << endl;
    	}
    public:
    	int a;
    private:
    	int b;
    protected:
    	int d;
    };
    class child3 : public parent
    {
    public:
    	child3(int c, int a, int b, int d) : parent(a, b, d), oop1(5, 6), oop2(7,8)
    	{
    		this->c = c;
    		cout << "派生类构造函数" << endl;
    	}
    	~child3()
    	{
    		cout << "派生类析构函数" << endl;
    	}
    public:
    	Grad oop1;
    	Grad oop2;
    private:
    	int c;
    protected:
    };
    int main()
    {
    	{
    		child3 oop(1, 2, 3, 3);
    	}
    	system("pause");
    	return 0;
    }