11.拷贝构造函数

#include <iostream>
using namespace std;

class Maker
{
private:
    int a;
public:
    Maker()
    {
        cout << "无参构造函数" << endl;
        a = 20;
    }
    //拷贝构造函数
    Maker(const Maker &m)
    {
        cout << "拷贝构造函数" << endl;
        a = m.a;
    }
    //打印函数
    void printfMaker()
    {
        cout << "a = " << a << endl;
    }
};

void test01()
{
    Maker m1;
    m1.printfMaker();

    //用一个已有的对象去初始化另一个对象
    Maker m2(m1);
    m2.printfMaker();
}

//2.编译器提供了默认的拷贝构造函数
class Maker2
{
private:
    int a;
public:
    Maker2()
    {
        cout << "无参构造函数" << endl;
        a = 20;
    }
    //编译器提供了默认的拷贝构造函数
    //Maker2(const Maker2 &m)
    //{
    //    //默认拷贝构造函数进行了成员变量的简单拷贝
    //    a = m.a;
    //}
    
    //打印函数
    void printfMaker2()
    {
        cout << "a = " << a << endl;
    }
};

void test02()
{
    Maker2 m1;
    m1.printfMaker2();

    Maker2 m2(m1);
    m2.printfMaker2();
}
//3.拷贝构造函数中形参要用引用
class Maker3
{
private:
    int ma;
public:
    Maker3(int Ma)
    {
        cout << "有参构造函数" << endl;
        ma = Ma;
    }
    Maker3(const Maker3 &m)
    {
        cout << "拷贝构造函数" << endl;
    }
};

void test03()
{
    Maker3 m1(10);//调用有参构造

    Maker3 m2(m1);//调用拷贝构造

    Maker3 m3 = m1;//调用拷贝构造

    //如果拷贝构造函数中的形参不是引用
    /*
    Maker3(const Maker3 m)//const Maker3 m = m1;  const Maker3 m(m1)
    {
        cout << "拷贝构造函数" << endl;
    }
    1.Maker3 m2(m1);
    2.const Maker3 m = m1;
    3.const Maker3 m(m1);
    4.const Maker3 m = m1;
    5.进入死循环
    */
}

int main()
{
    test01();
    system("pause");
    return EXIT_SUCCESS;
}

参考资料

参考资料来源于黑马程序员等