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49. The copy constructor and overloaded 】

2022-07-31 14:09:00 【Lee is struggling...】

【The default copy constructor is called when no explicit copy constructor is provided】

#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; // Use the initialization method
   s1.show();
   cout << "***********************" << endl;
   Student s2(s); // Assign values using parentheses
   s2.show();
   return 0;

}

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【When explicitly providing a copy constructor】

#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) //The copy constructor uses a reference ,Because a pass-by-reference parameter changes, the actual parameter also changes

{

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; // Use the initialization method

s1.show();

cout << "***********************" << endl;

Student s2(s); // Assign values using parentheses

s2.show();

return 0;

}

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【Copy constructor and overloaded operator functions】

(Why return the object name,It's actually using a copy constructor)

#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 << "*************An overloaded operator was called**********" << endl;
       Complex c1;
       c1.real = real + c.real; // Returns the real part of the object=original real department+Quote the real part;
       c1.imag = imag + c.imag;
       return c1; //返回对象名,In fact, I want to use the copy function
   }
   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();
}