Copy Control Example

复制构造函数, 赋值操作符 operator = ,析构函数 总称为复制控制 (Copy Control)

e.g.:

Code:

#include <iostream>

using namespace std;

class T{
public:
    T(){ cout<<"T constructor."<<endl; }
    T(const T& tobj){
        cout<<" T copy construct from T:"<<&tobj<<endl;
        t=tobj.t;
    }
    //若声明为explicit,则隐式调用
     /*explicit */
    T(int tmp):t(tmp){
         cout<<"T constructor from int."<<tmp<<endl;
    }
    ~T(){   cout<<"T destructor. instance:"<<(int)this<<",t value:"<<t<<endl;   }
    T& operator =(const T& tobj){
        cout<<" operator =, from:"<<hex<<&tobj<<",to:"<<hex<<(int)this<<endl;
        this->t=tobj.t;
        return *this;
    }
    //前自加操作符
    T& operator ++(){
        ++t;
        return *this;
    }
    //后自加操作符
    T operator ++(int){
        T tmp(*this);
        ++ this->t;
        return tmp;
    }
    void print(){
        cout<<"addr:0x"<<hex<<(int)this<<".t="<<t<<endl;
    }
private:
    int t;
};


int main()
{
    T t=1;
    //t.print();
    t=2;    //生成一个临时对象 tmp(2),再调用operator =方法,将其值赋给t
    //t.print();
/*
    cout<<"T 自加之前"<<endl;
    t.print();
    ++t;
    cout<<"T 自加之后"<<endl;
    t.print();

    T t2=++t;
    t.print();
    t2.print();
*/
    cout<<"后加操作测试"<<endl;
    T t3= t++;
    t.print();
    t3.print();

    cin.get();
    return 0;
}