构造函数与析构函数-蒲公英云

构造函数与析构函数

/*构造函数--组合和继承*/
/*一般来说子类不继承父类的构造函数*/ 
#include <iostream>
using namespace std;
class Base1{
    public:
        Base1(int i){  //基类Base1,构造函数有参 
            cout << "Constructing Base1 " << i << endl; 
        }
};
class Base2{
    public:
        Base2(int j){  //基类Base2,构造函数有参 
            cout << "Constructing Base2 " << j << endl; 
        }
};
class Base3{
    public:
        Base3(){  //基类Base3,构造函数无参 
            cout << "Constructing Base3* " << endl; 
        }
}; 
class Derived:public Base2, public Base1, public Base3{ //注意基类名继承的顺序 
    public:
        Derived(int a, int b, int c, int d):Base1(a), member2(d), member1(c), Base2(b){}
    private:
        Base1 member1;
        Base2 member2;
        Base3 member3;
}; 
int main(){
    Derived obj(1, 2, 3, 4);//执行时候先初始化基类的构造函数，执行顺序按照派生类公有继承基类的顺序 
    return 0;               //所以先执行Base2(2), 再执行Base1(1),最后执行无参的Base3; 
}                           //再者初始化私有成员类的对象，按照member1(3), member2(4),member3的顺序

/*构造函数的析构函数--和构造函数一样不被子类继承*/ 
#include <iostream>
using namespace std;
class Base1{
    public:
        Base1(int i){  //基类Base1,构造函数有参 
            cout << "Constructing Base1 " << i << endl; 
        }
        ~Base1(){
            cout << "Destructing Base1" << endl; 
        } 
};
class Base2{
    public:
        Base2(int j){  //基类Base2,构造函数有参 
            cout << "Constructing Base2 " << j << endl; 
        }
        ~Base2(){
            cout << "Destructing Base2" << endl;
        } 
};
class Base3{
    public:
        Base3(){  //基类Base3,构造函数无参 
            cout << "Constructing Base3* " << endl; 
        }
        ~Base3(){
            cout << "Destructing Base3" << endl;
        } 
}; 
class Derived:public Base2, public Base1, public Base3{ //注意基类名继承的顺序 
    public:
        Derived(int a, int b, int c, int d):Base1(a), member2(d), member1(c), Base2(b){}
    private:
        Base1 member1; //析构函数首先在结束时析构本类的对象成员，但执行顺序和构造函数相反，从最后的member3~member1这个顺序执行 
        Base2 member2;//然后再析构基类的对象，析构的顺序按照公有继承顺序的反方向，先Base3再Base1最后Base2 
        Base3 member3;
}; 
int main(){
    Derived obj(1, 2, 3, 4);//执行时候先初始化基类的构造函数，执行顺序按照派生类公有继承基类的顺序 
    return 0;               //所以先执行Base2(2), 再执行Base1(1),最后执行无参的Base3; 
}                           //再者初始化私有成员类的对象，按照member1(3), member2(4),member3的顺序