C++拷贝构造函数

C++拷贝构造函数

文章目录

1.拷贝构造函数2.调用父类的拷贝构造函数3.拷贝构造函数与浅拷贝

1.拷贝构造函数

拷贝构造函数是构造函数的一种。

当利用已存在的对象创建一个新对象时（类似于拷贝），就会调用新对象的拷贝构造函数进行初始化。

拷贝构造函数的格式是固定的，接收一个const引用作为参数。

#include 
using namespace std;

class Car {
public:
	int m_price;
	int m_length;
	Car(int price = 0, int length = 0) : m_price(price), m_length(length) {
		cout << "Car(int price = 0, int length = 0)" << endl;
	}

	void display() {
		cout << "price = " << m_price << ", length = " << m_length << endl;
	}
};

int main() {

	Car car1(100, 5);
	Car car2(car1);
	car2.display();

	getchar();
	return 0;
}

#include 
using namespace std;

class Car {
public:
	int m_price;
	int m_length;
	Car(int price = 0, int length = 0) : m_price(price), m_length(length) {
		cout << "Car(int price = 0, int length = 0)" << endl;
	}

	// 拷贝构造函数
	Car(const Car &car) : m_price(car.m_price), m_length(car.m_length) {
		cout << "Car(const Car &car)" << endl;
	}

	void display() {
		cout << "price = " << m_price << ", length = " << m_length << endl;
	}
};

int main() {

	Car car1(100, 5);
	Car car2(car1);
	car2.display();

	getchar();
	return 0;
}

2.调用父类的拷贝构造函数

#include 
using namespace std;

class Person {
public:
	int m_age;
	Person(int age = 0) : m_age(age) {}
	Person(const Person &person) : m_age(person.m_age) {}
};

class Student : public Person {
public:
	int m_score;
	Student(int age = 0, int score = 0) : Person(age), m_score(score) {}
	Student(const Student &student) : Person(student), m_score(student.m_score) {}
};

int main() {

	Student stu1(18, 100);
	Student stu2(stu1);

	cout << stu2.m_age << endl; // 18
	cout << stu2.m_score << endl; // 100

	getchar();
	return 0;
}

3.拷贝构造函数与浅拷贝

#include 
using namespace std;

class Car {
	int m_price;
	int m_length;
public:
	Car(int price = 0, int length = 0) : m_price(price), m_length(length) {
		cout << "Car(int price = 0, int length = 0)" << endl;
	}

	Car(const Car &car) : m_price(car.m_price), m_length(car.m_length) {
		cout << "Car(const Car &car)" << endl;
	}

	void display() {
		cout << "price = " << m_price << ", length = " << m_length << endl;
	}
};

int main() {
	
	Car car1(100, 5); // Car(int price = 0, int length = 0)
	Car car2(car1); // Car(const Car &car)
	Car car3 = car2; // Car(const Car &car)
	Car car4; // Car(int price = 0, int length = 0)

	car4.display(); // price = 0, length = 0

	// 这里并没有调用拷贝构造函数（仅仅是简单的赋值操作，默认是浅拷贝）
	car4 = car3;

	car4.display(); // price = 100, length = 5

	getchar();
	return 0;
}