c++官方文档-copy constructor

#include <iostream>
using namespace std;

class Example5
{
        string* ptr;
    public:
        Example5(const string& str):ptr(new string(str)){}
        ~Example5(){delete ptr;}
        //copy constructor
        Example5(const Example5& x):ptr(new string(x.content())){
            cout<<"copy constructor"<<endl;
        }
        //access content;
        const string& content()const{return *ptr;}
};

int main()
{
    Example5 foo("Example");
    Example5 bar = foo;
    cout<<"bar's content:"<<bar.content()<<'\n';
    return ;
}