拷贝构造函数
拷贝构造函数是使用类对象的引用作为参数的构造函数，它能够将参数的属性值拷贝给新的对象，完成新对象的初始化。
通常在一下三种情况下，程序会自动调用拷贝构造函数。
1.使用一个对象初始化另一个对象
#include <iostream>
#include<string>
using namespace std;
class Car
{
public:
Car(){}; //初始化构造函数
Car(string name, int seats);
Car(Car &con_refcar);
~Car(); //析构函数
private:
string m_name;
int m_seats;
};
Car::Car(string name, int seats)
{
m_name = name;
m_seats = seats;
}
Car::Car(Car &con_refcar)
{
m_name = con_refcar.m_name;
m_seats = con_refcar.m_seats;
}
Car::~Car() {}
int main()
{
Car mynewcar("rrrr2", 4);
Car myseccar(mynewcar); //用一个对象对另一个对象初始化
return 0;
}
2.对象作为实参传递给函数参数
#include <iostream>
#include<string>
using namespace std;
class Car
{
public:
Car(){}; //初始化构造函数
Car(string name, int seats);
Car(Car &con_refcar);
void print();
~Car(); //析构函数
private:
string m_name;
int m_seats;
};
Car::Car(string name, int seats)
{
m_name = name;
m_seats = seats;
}
Car::Car(Car &con_refcar)
{
m_name = con_refcar.m_name;
m_seats = con_refcar.m_seats;
}
Car::~Car() {}
void Car::print()
{
cout<<"name: "<<m_name<<endl;
cout<<"sizes: "<<m_seats<<endl;
}
void print_carinfo(Car carinfo) //对象最为实参传递给函数
{
carinfo.print();
}
int main()
{
Car mynewcar("rrrr2", 4);
print_carinfo(mynewcar); //调用该函数
return 0;
}
3.函数返回值为类对象，创建临时对象作为返回值
#include <iostream>
#include<string>
using namespace std;
class Car
{
public:
Car(){}; //初始化构造函数
Car(string name, int seats);
Car(Car &con_refcar);
Car get_carinfo(); //****
void print();
~Car(); //析构函数
private:
string m_name;
int m_seats;
};
Car::Car(string name, int seats)
{
m_name = name;
m_seats = seats;
}
Car::Car(Car &con_refcar)
{
m_name = con_refcar.m_name;
m_seats = con_refcar.m_seats;
}
Car::~Car()
{
}
void Car::print()
{
cout<<"name: "<<m_name<<endl;
cout<<"sizes: "<<m_seats<<endl;
}
Car Car::get_carinfo() //关键函数
{
Car tmp(m_name, m_seats); //定义类对象
return tmp; //返回类对象
}
int main()
{
Car mynewcar("rrrr2", 4);
Car ret;
ret = mynewcar.get_carinfo(); //ret接受返回的类对象
ret.print();
return 0;
}
以上都是浅拷贝, 浅拷贝有个特点就是：类的私有成员不需要new出新的空间，像上面的m_name都是用string类型；如果换成char类型，上面的程序就会出错，原因是，浅拷贝并未为拷贝对象开辟空间，只是让拷贝对象的地址指向被拷贝对象的地址，相当于“引用”。为了解决这个问题，就要用到深拷贝！
深拷贝
#include <iostream>
#include<string>
using namespace std;
class Car
{
public:
Car(char *name, int seats);
Car(Car &con_refcar);
~Car();
private:
char *m_name; //char型数据成员
int m_seats;
};
Car::Car(char *name, int seats)
{
int len = strlen(name) + 1;
m_name = new char[len]; //每个对象初始化都要临时开劈空间
strcpy(m_name, name ); //字符串之间赋值要用strcpy()函数
m_seats = seats;
}
Car::Car(Car &con_refcar) //深拷贝
{
m_name = new char[strlen(con_refcar.m_name)+1]; //浅拷贝无需开劈空间，数据成员赋值需要开辟空间的都只能用深拷贝实现！
strcpy(m_name,con_refcar.m_name);
m_seats = con_refcar.m_seats;
}
Car::~Car()
{
delete[] m_name;
}
int main()
{
char c[] = "rrrr2";
Car mynewcar(c, 4);
Car myseccar(mynewcar);
return 0;
}
若有错，望指出
