C++类构造析构调用顺序训练(复习专用)

Posted 2020-06-13

//对象做函数参数
//1 研究拷贝构造 
//2 研究构造函数，析构函数的调用顺序

//总结 构造和析构的调用顺序

#include "iostream"
using namespace std;

class ABCD
{ //this（）
public:
	ABCD(int a, int b, int c)
	{
		this->a = a;
		this->b = b;
		this->c = c;
		printf("ABCD() construct, a:%d,b:%d,c:%d  \n", this->a, this->b, this->c);
	}
	~ABCD()
	{
		printf("~ABCD() construct,a:%d,b:%d,c:%d  \n", this->a, this->b, this->c);
	}
	int getA()
	{
		return this->a;
	}
protected:
private:
	int a;
	int b;
	int c;
};


class MyE
{
public:
	MyE() :abcd1(1, 2, 3), abcd2(4, 5, 6), m(100)
	{
		cout << "MyD()" << endl;
	}
	~MyE()
	{
		cout << "~MyD()" << endl;
	}
	MyE(const MyE & obj) :abcd1(7, 8, 9), abcd2(10, 11, 12), m(100)
	{
		printf("MyD(const MyD & obj)\n");
	}

protected:
	//private:
public:
	ABCD abcd1; //c++编译器不知道如何构造abc1
	ABCD abcd2;
	const int m;

};

int doThing(MyE mye1)
{
	printf("doThing() mye1.abc1.a:%d \n", mye1.abcd1.getA());
	return 0;
}

int run2()
{
	MyE myE;
	doThing(myE);
	return 0;
}

//
int run3()
{
	printf("run3 start..\n");

	ABCD abcd = ABCD(100, 200, 300); //用临时对象来初始化一个对象,就会把临时对象变化成要初始化的对象,而不会调用copy构造函数,临时对象也不用将自己赋值给对方,然后自己销毁这么麻烦.



	//ABCD(400, 500, 600); //临时对象的生命周期
	printf("run3 end\n");
	return 0;
}

int main()
{
	run2();
	//run3();
	system("pause");
	return 0;
}

　　

输出\