C++ 类的赋值运算时，构造函数的调用
#include <iostream>
using namespace std;
class Box
{
int length;
std::string name = "box_default";
public:
Box(std::string s) {
name = s;
std::cout << "Default constructor: "<< name << std::endl;
}
Box(const Box& b) {
std::cout << "Copy constructor: "<< b.name << ", length: " << b.length << std::endl;
std::cout << "Copy constructor : this : " << this->name << std::endl;
this->length = b.length;
this->name = "box_copy";
std::cout << "Copy constructor end: this : " << this->name << ", b : " << b.name << std::endl;
}
int getLength(void)
{
return length;
}
void setLength(int len)
{
length = len;
}
// 重载 + 运算符，用于把两个 Box 对象相加
Box operator+(const Box& b)
{
Box box("box+");
box.length = this->length + b.length;
std::cout << "operator+: this: " << this->name << " ,b: " << b.name << std::endl;
return box;
}
Box& operator = (const Box& b) {
std::cout << "operator=: this: " << this->name << ", b: " << b.name << std::endl;
std::cout << "length: " << b.length << std::endl;
this->name = b.name;
this->length = b.length;
return *this;
}
};
// 程序的主函数
int main()
{
Box Box1("box1"); // 声明 Box1，类型为 Box
Box Box2("box2"); // 声明 Box2，类型为 Box
Box Box3("box3"); // 声明 Box3，类型为 Box
// Box1 详述
Box1.setLength(6);
// Box2 详述
Box2.setLength(12);
// Box1
cout << "Length of Box1 : " << Box1.getLength() << endl;
// Box2
cout << "Length of Box2 : " << Box2.getLength() << endl;
// 把两个对象相加，得到 Box3
Box3 = Box1 + Box2;
// Box3
cout << "Length of Box3 : " << Box3.getLength() << endl;
return 0;
}