C++构造函数初始化顺序详解(2)

时间:2014-10-02 11:04来源:网络整理作者:网络点击: 次

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class OBJ1 { public: OBJ1() { cout "OBJ1\n"; } }; class OBJ2 { public: OBJ2() { cout "OBJ2\n"; } }; class Base1 { public: Base1() { cout "Base1\n"; } }; class Base2 { public: Base2() { cout "Base2\n";

class OBJ1
{
public:
    OBJ1()
    {
        cout << "OBJ1\n";
    }
};

class OBJ2
{
public:
    OBJ2()
    {
        cout << "OBJ2\n";
    }
};

class Base1
{
public:
    Base1()
    {
        cout << "Base1\n";
    }
};

class Base2
{
public:
    Base2()
    {
        cout << "Base2\n";
    }
};

class Base3
{
public:
    Base3()
    {
        cout << "Base3\n";
    }
};

class Base4
{
public:
    Base4()
    {
        cout << "Base4\n";
    }
};

class Derived : public Base1, virtual public Base2,
    public Base3, virtual public Base4
{
public:
    Derived() : Base4(), Base3(), Base2(),
        Base1(), obj2(), obj1()
    {
        cout << "Derived.\n";
    }
protected:
    OBJ1 obj1;
    OBJ2 obj2;
};

void test()
{
Derived aa;
cout << "This is ok.\n";
}

int main()
{
test();
return 0;
}
/*
Base2
Base4
Base1
Base3
OBJ1
OBJ2
Derived.
This is ok.
*/

【代码2】

复制代码代码如下:

/*
version: 1.0
author: hellogiser
date: 2014/9/27
*/

#include "stdafx.h"
#include <iostream>
using namespace std;

class Base1
{
public:
    Base1(int i)
    {
        cout << "Base1 " << i << endl;
    }
};

class Base2
{
public:
    Base2(int i)
    {
        cout << "Base2 " << i << endl;
    }
};

class Base3
{
public:
    Base3()
    {
        cout << "Base3 *" << endl;
    }
};

class Derived : public Base2, public Base1, virtual public Base3
{
public:
    Derived(int a, int b, int c, int d, int e)
        : Base1(a), b2(d), b1(c), Base2(b)
    {
        m = e;
        cout << "Derived.\n";
    }
protected:
    Base1 b1;
    Base2 b2;
    Base3 b3;
    int m;
};

void test()
{
Derived aa(1, 2, 3, 4, 5);
cout << "This is ok.\n";
}

int main()
{
test();
return 0;
}
/*
Base3 *
Base2 2
Base1 1
Base1 3
Base2 4
Base3 *
Derived.
This is ok.
*/

分析：

(1) virtual

按照继承顺序：Base3

第一步：先继承Base3,在初始化列表里找不到Base3(), 则调用Base3里的默认构造函数Base3()，打印"Base3 *"

(2)non-virtual

按照继承顺序：Base2，Base1

第二步：继承Base2,在初始化列表中找Base2(b)，调用Base2的构造函数Base2(2)，打印"Base2 2"

第三步：继承Base1,在初始化列表中找Base1(a)，调用Base1的构造函数Base1(1)，打印"Base1 1"

(3)data member

按照申明顺序：b1,b2,b3