派生类初始化顺序

最新推荐文章于 2024-05-22 20:03:03 发布

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最新推荐文章于 2024-05-22 20:03:03 发布

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CC 4.0 BY-SA版权

文章标签： C C++ C#

本文链接：https://blog.youkuaiyun.com/weihe6666/article/details/83853966

本文详细解析了C++中多重继承与虚基类的概念及使用方法，通过具体的代码实例展示了不同类型的基类如何被正确初始化，并解释了构造顺序与析构顺序的重要性。

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#include<iostream>
using namespace std;

class B1
{
public:
 B1()
 {
	 cout << "call B1" << endl;
 }
};

class V1 : public B1
{
public:
	V1()
	{
		cout << "call V1" << endl;
	}
	~V1()
	{
		cout << "call ~V1" << endl;
	}
};

class D1 : virtual public V1
{
public:
 	D1()
	{
		cout << "call D1" << endl;
	}
	~D1()
	{
		cout << "call ~D1" << endl;
	}
};

class B2
{
public:
	B2()
	{
		cout << "call B2" << endl;
	}
	~B2()
	{
		cout << "call ~B2" << endl;
	}
};

class B3
{
public:
	B3()
	{
		cout << "call B3" << endl;
	}
	~B3()
	{
		cout << "call ~B3" << endl;
	}
};
class V2 : public B1, public B2
{
public:
	V2()
	{
		cout << "call V2" << endl;
	}
	~V2()
	{
		cout << "call ~V2" << endl;
	}
};

class D2 : virtual public V2 ,public B3
{
public:
	D2()
	{
		cout << "call D2" << endl;
	}
	~D2()
	{
		cout << "call ~D2" << endl;
	}
};

class M1
{
public:
	M1()
	{
		cout << "call M1" << endl;
	}
	~M1()
	{
		cout << "call ~M1" << endl;
	}
};
class M2
{
public:
	M2()
	{
		cout << "call M2" << endl;
	}
	~M2()
	{
		cout << "call ~M2" << endl;
	}
};

class X : public D1,public D2
{
public:
		X()
	{
		cout << "call X" << endl;
	}
	~X()
	{
		cout << "call ~X" << endl;
	}
	M1 m1_;
	M2 m2_;
};


void main()
{
	X b;

}

输出：
call B1
call V1
call B1
call B2
call V2
call D1
call B3
call D2
call M1
call M2
call X
析构函数于此相反。

X对象各子对象的构造顺序如下：
1.首先：构造虚基子类对象：
构造V1：B1：：B1()V1：：V1()
构造V2:B1::B1() B2::B2() V2::V2()
2.其次，构造非虚基类子对象：
构造 D1:D1::D1()
构造 D2:B3::B3() D2::D2()
3.再次，构造所有成员：
M1::M1()
M2::M2()
4. 构造X本身：
X::X()