C++中复制构造函数和隐式转换

2019独角兽企业重金招聘Python工程师标准>>>

隐式转换可能发生在对象的初始化中（包括由赋值间接产生的初始化），不可能由赋值直接产生

#include <iostream>

using namespace std;

class MyClass
{
public:
    MyClass();
    MyClass(int i);
    MyClass(const MyClass &c);
    ~MyClass();
    MyClass & operator = (const MyClass &c);

private:
    int m_i;
};

MyClass::MyClass()
{
    m_i = 0;
    cout << "MyClass()" << endl;
}

MyClass::MyClass(int i)
{
    m_i = i;
    cout << "MyClass(int i)" << endl;
}

MyClass::MyClass(const MyClass &c)
{
    m_i = c.m_i;
    cout << "MyClass(const MyClass &c)" << endl;
}

MyClass::~MyClass()
{

}

MyClass & MyClass::operator =(const MyClass &c)
{
    m_i = c.m_i;
    cout << "operator =(const MyClass &c)" << endl;
    return *this;
}

int main()
{
    MyClass c1;     // MyClass()
    cout << "-------------------------------" << endl;
    MyClass c2 = 2; // MyClass(int i) 隐式转换
    cout << "-------------------------------" << endl;
    MyClass c3 = c2;// MyClass(const MyClass &c) 隐式转换
    cout << "-------------------------------" << endl;
    c1 = 2;         // MyClass(int i) 隐式转换
                    // operator =(const MyClass &c) 无隐式转换
    cout << "-------------------------------" << endl;
    c3 = c2;        // operator =(const MyClass &c) 无隐式转换
    cout << "-------------------------------" << endl;
    return 0;
}

结果：

MyClass()

-------------------------------

MyClass(int i)

-------------------------------

MyClass(const MyClass &c)

-------------------------------

MyClass(int i)

operator =(const MyClass &c)

-------------------------------

operator =(const MyClass &c)

-------------------------------

转载于:https://my.oschina.net/xiangxw/blog/114402