【没有明确提供拷贝构造函数的时候回调用默认的拷贝构造函数】
#include <iostream>
#include <string.h>
using namespace std;
class Student
{
private:
int number;
string name;
public:
Student(int nu, string na) :number(nu), name(na) {}
Student() {}
void show()
{
cout << "学生的学号是:" << number << "学生的姓名是:" << name << endl;
}
};
int main()
{
Student s(21032114, "李威涛");
Student s1 = s; // 利用初始化的方法
s1.show();
cout << "***********************" << endl;
Student s2(s); // 利用小括号的方法赋值
s2.show();
return 0;
}
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【明确提供拷贝构造函数时】
#include <iostream>
#include <string.h>
using namespace std;
class Student
{
private:
int number;
string name;
public:
Student(int nu, string na) :number(nu), name(na) {}
Student() {}
Student(const Student& s) //拷贝构造函数要用用引用 ，因为引用值传递形参改变实参也改变
{
number = s.number;
name = s.name;
}
void show()
{
cout << "学生的学号是:" << number << "学生的姓名是:" << name << endl;
}
};
int main()
{
Student s(21032114, "李威涛");
Student s1 = s; // 利用初始化的方法
s1.show();
cout << "***********************" << endl;
Student s2(s); // 利用小括号的方法赋值
s2.show();
return 0;
}
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【拷贝构造函数与重载运算符函数】
(为什么要返回对象名，实际上是在用拷贝构造函数)
#include <iostream>
using namespace std;
class Complex
{
private:
double real;
double imag;
public:
Complex(double r, double i) :real(r), imag(i) { cout << "调用了构造函数" << endl; }
Complex() {}
Complex(const Complex& c)
{
real = c.real;
imag = c.imag;
cout << "*************调用了拷贝构造函数:************" << endl;
}
Complex operator+(Complex& c)
{
cout << "*************调用了重载运算符**********" << endl;
Complex c1;
c1.real = real + c.real; // 返回对象的实部=原实部+引用实部；
c1.imag = imag + c.imag;
return c1; //返回对象名，其实是想用拷贝函数
}
void show()
{
cout << "加到一起是:" << real << "+" << imag << "i" << endl;
}
};
int main()
{
Complex c(2, 3), c1(c);
c1.show();
Complex c2(3, 4), c3(2, 5),c4;
c4 = c2.operator+(c3); // 实际上为： c4=c1(real,imag);
c4.show();
}
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【在重载运算符的时候，如果不调用新的对象，要返回*this】
#include <iostream>
using namespace std;
class Complex
{
private:
double real;
double imag;
public:
Complex(double r, double i) :real(r), imag(i) { cout << "调用了构造函数" << endl; }
Complex() {}
Complex(const Complex& c)
{
real = c.real;
imag = c.imag;
cout << "*************调用了拷贝构造函数:************" << endl;
}
Complex operator=(Complex& c)
{
cout << "*************调用了重载运算符**********" << endl;
real = c.real; // 返回对象的实部=原实部+引用实部；
imag = c.imag;
return *this; //临时变量后面会消失
}
void show()
{
cout << "加到一起是:" << real << "+" << imag << "i" << endl;
}
};
int main()
{
Complex c(2, 3), c1(c);
c1.show();
Complex c2(3, 4), c3(2, 5),c4;
c2.operator=(c3); //
c2.show();
}
