强化训练2--匿名对象的生命周期

//临时对象和匿名对象没有人去接它，编译器马上就析构了

#include<iostream>
using namespace std;

class ABCD
{
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:
ABCD abcd1;//c++编译器不知道如何构造abcd1；先执行这个函数的构造函数
ABCD abcd2;
const int m;
};
int doThing(MyE mye1)
{
//printf("doThing() mye1,abcd1,a:%d \n",mye1.abcd1.getA());//有问题一直通过不了
printf("doThing() mye1,abcd1,a:%d \n");
return 0;
}

int run3()
{
printf("run3 star..\n");

ABCD(400,500,600);//临时对象的生命周期，直接调用ABCD类的构造函数
//临时对象和匿名对象没有人去接它，编译器马上就析构了printf("run3 end..\n");
return 0;
}

int main()
{

run3();

system("pause");
return 0;
}

匿名对象转正

#include<iostream>
using namespace std;

class ABCD
{
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:
ABCD abcd1;//c++编译器不知道如何构造abcd1；先执行这个函数的构造函数
ABCD abcd2;
const int m;
};
int doThing(MyE mye1)
{
//printf("doThing() mye1,abcd1,a:%d \n",mye1.abcd1.getA());//有问题一直通过不了
printf("doThing() mye1,abcd1,a:%d \n");
return 0;
}

/*int run3()
{
printf("run3 star..\n");
//这个时候没有创建一个对象
ABCD(400,500,600);//临时对象的生命周期，直接调用ABCD类的构造函数
//临时对象和匿名对象没有人去接它，编译器马上就析构了printf("run3 end..\n");
return 0;
}*/

int run3()
{
printf("run3 star..\n");
//这个时候创建一个对象
ABCD abcd=ABCD(400,500,600);
//有对象去接了
printf("run3 end..\n");
return 0;
}

int main()
{

run3();

system("pause");
return 0;
}