c++ - 如何显示我自己的数据类型的 std::vector 的内容并使用 std::copy 在控制台上显示名称？

Question

我想显示 std::vector<User> 的内容使用std::copy与我通过 std::for_each 实现的方式类似在下面的代码中。

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
class User {
private:
    std::string m_sName;
public:
    User(std::string sName):m_sName(sName) {}
    std::string GetName()const {
        return m_sName;
    }
};
int main()
{
    std::vector<User> vectNames;
    vectNames.emplace_back("Jack");
    vectNames.emplace_back("George");
    vectNames.emplace_back("Jose");
//How can I get std::copy to do what the std::for_each is doing?
    std::copy(vectNames.begin(), vectNames.end(), std::ostream_iterator<User>(std::cout, "\n"));
//The following line is what I really would like std::copy to do. 
    std::for_each(vectNames.begin(), vectNames.end(), [](const User &user) {std::cout << user.GetName() << "\n"; });
    
}

Answer 1

您可以简单地重载ostream运算符:

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

class User {
private:
    std::string m_sName;
public:
    User(std::string sName):m_sName(sName) {}
    std::string GetName()const {
        return m_sName;
    }
    void print(std::ostream& where) const
        { where << m_sName; }
};

/// Overloaded ostream operator
std::ostream& operator<< (std::ostream& out, const User& user)
{
    user.print(out);
    return out;
}

int main()
{
    std::vector<User> vectNames;
    vectNames.emplace_back("Jack");
    vectNames.emplace_back("George");
    vectNames.emplace_back("Jose");
    
    std::copy(vectNames.begin(), vectNames.end(), std::ostream_iterator<User>(std::cout, "\n"));
}

一般来说，我总是有一个重载的ostream作为存储和输出信息的类的一部分。