派生类构造函数的理解

我大概试了派生类构造函数的所有情况吧，怕忘掉所以在这里整理一下
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第一种就是书上例题上的那种最简单的情况

#include<iostream>
using namespace std;
class Base1{
    public:
        Base1(int i){cout<<"Constructing Base1"<<i<<endl;
        }
        ~Base1(){cout<<"Destroying Base1"<<endl;}
};
class Base2{
    public:
        Base2(int j){cout<<"Constructing Base2"<<j<<endl;
        }
        ~Base2(){cout<<"Destroying Base2"<<endl;
        }
};
class Base3{
    public:
        Base3(){cout<<"Constructing Base3*"<<endl;
        }
        ~Base3(){cout<<"Destroying Base3*"<<endl;
        }
};
class Derived:public Base2,public Base1,public Base3{
    public:
        Derived(int a,int b,int c,int d):Base1(a),member2(d),member1(c),Base2(b){
        }
        ~Derived(){cout<<"Destroying Derived"<<endl;
        }
        private:
            Base1 member1;
            Base2 member2;
            Base3 member3;
};
int main()
{
    Derived obj(1,2,3,4);
    return 0;
}

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第二种，我把继承方式换成了私有继承（这里容易形成的误区就是类的对象不是不能调用私有成员吗，那只是对继承下来的那些东西的限制吧，毕竟构造函数是不能继承的）

#include<iostream>
using namespace std;
class Base1{
    public:
        Base1(int i){cout<<"Constructing Base1"<<i<<endl;
        }
        ~Base1(){cout<<"Destroying Base1"<<endl;}
};
class Base2{
    public:
        Base2(int j){cout<<"Constructing Base2"<<j<<endl;
        }
        ~Base2(){cout<<"Destroying Base2"<<endl;
        }
};
class Base3{
    public:
        Base3(){cout<<"Constructing Base3*"<<endl;
        }
        ~Base3(){cout<<"Destroying Base3*"<<endl;
        }
};
class Derived:private Base2,private Base1,private Base3{
    public:
        Derived(int a,int b,int c,int d):Base1(a),member2(d),member1(c),Base2(b){
        }
        ~Derived(){cout<<"Destroying Derived"<<endl;
        }
        private:
            Base1 member1;
            Base2 member2;
            Base3 member3;
};
int main()
{
    Derived obj(1,2,3,4);
    return 0;
}

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第三种，就是最全面的一种了，我把Derived的构造函数体里加了内容

#include<iostream>
using namespace std;
class Base1{
    public:
        Base1(int i){cout<<"Constructing Base1"<<i<<endl;
        }
        ~Base1(){cout<<"Destroying Base1"<<endl;}
};
class Base2{
    public:
        Base2(int j){cout<<"Constructing Base2"<<j<<endl;
        }
        ~Base2(){cout<<"Destroying Base2"<<endl;
        }
};
class Base3{
    public:
        Base3(){cout<<"Constructing Base3*"<<endl;
        }
        ~Base3(){cout<<"Destroying Base3*"<<endl;
        }
};
class Derived:public Base2,public Base1,public Base3{
    public:
        Derived(int a,int b,int c,int d):Base1(a),member2(d),member1(c),Base2(b)
        { 
        cout<<"Constructing Derived"<<endl;
        }
        ~Derived(){cout<<"Destroying Derived"<<endl;
        }
        private:
            Base1 member1;
            Base2 member2;
            Base3 member3;
};
int main()
{
    Derived obj(1,2,3,4);
    return 0;
}

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下面这个也没什么了，就是比较复杂而已（因为嵌套了一些）
//这里C继承B和A，内嵌D，E继承C；调用构造函数情况：

#include<iostream>
using namespace std ;
class D
{
public:
    D(){cout<<"initializing D..."<<endl;}
    ~D(){cout<<"destroying D..."<<endl;}
};
class A
{ 
public:
    A(){cout<<"initializing A..."<<endl;}
    ~A(){cout<<"destroying A..."<<endl;}
};
class B
{
public:
    B(){cout<<"initializing B..."<<endl;}
    ~B(){cout<<"destroying B..."<<endl;}
};
class C : private B  , private A 
{
public:
    D d;
    C(){cout<<"initializing C..."<<endl;}
    ~C(){cout<<"destroying C..."<<endl;}
};
class E: private C
{
public:
    E(){cout<<"initializing E..."<<endl;}
    ~E(){cout<<"destroying E..."<<endl;}
};
int main()
{
    E e;  
    return 0 ;
}

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总结：
多重继承和有内嵌对象时构造函数调用顺序
1、调用按照声明顺序的基类构造函数 2、调用内嵌对象构造函数 3、调用自身构造函数
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还有就是一些注意点吧
首先必须清楚一点：初始化与赋值是两码事！

派生类的构造函数的初始化列表可以包含基类的构造函数、派生类成员的初始化，但是不能有基类成员的初始化！