为什么绑定函数不适用于解引用迭代器？

Question

我是 C++ 编程新手。我正在使用 bind 函数将对象与 class setter 绑定并调用 setter。当我尝试将迭代器取消引用为 bind 函数中的对象时，对象变量没有改变。但是，当我只是将迭代器作为 bind 函数中的对象传入时，它就起作用了。谁能给我解释一下这是为什么？

string name;
char temp;
bool manager;

cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
cout << "Employee Name: ", getline(cin, name, '\n');

auto employee = find(employee_list.begin(), employee_list.end(), name);
if (employee != employee_list.end()){

    cout << "Change Detail " << endl;
    cout << "1. Name" << endl;
    cout << "2. Phone" << endl;
    cout << "3. Address" << endl;

    string choice;
    string new_value;
    map<string, function<void(string_view)>> subMenu;

    do{
        cout << "Selection: ", cin >> choice;

        cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        cout << "New Value: ", getline(cin, new_value, '\n');

        subMenu = {
            {"1", bind(&Employee::set_name, *employee, new_value)},
            {"2", bind(&Employee::set_phone, *employee, new_value)},
            {"3", bind(&Employee::set_address, *employee, new_value)}
        };

        if(subMenu.find(choice) == subMenu.end()){
            cout << "\nSelection Not Found\n" << endl;
        }
    }
    while (subMenu.find(choice) == subMenu.end());

    auto selection = subMenu.find(choice)->second;
    selection(new_value);

    cout << "Operation complete" << right << endl;  
}

Setter 函数：

void Employee::set_name(std::string_view p_name){
    std::cout << "Set Name: " << std::endl;
    std::cout << "Old value: " << name << std::endl;
    name = p_name;
    std::cout << "New value: " << name << std::endl;
    
}

void Employee::set_phone(std::string_view p_phone){
    phone = p_phone;
}

void Employee::set_address(std::string_view p_address){
    address = p_address;
}

当我尝试使用*employee时，它并没有改变对象的变量。但是，当我只传入 find 函数返回的迭代器 (employee) 时，它起作用了，但我不明白。我知道我可以用 if/else 语句轻松做到这一点，但我想了解更多关于 c++ 的知识。

Answer 1

如 cpprefrence 的 std::bind 页面所述：

The arguments to bind are copied or moved, and are never passed by reference unless wrapped in std::ref or std::cref.

如果你想改变*employee指向的对象，你应该将它们包裹在std::reference_wrapper中，例如通过辅助函数 std::ref:

subMenu = {
    {"1", bind(&Employee::set_name, std::ref(*employee), new_value)},
    {"2", bind(&Employee::set_phone, std::ref(*employee), new_value)},
    {"3", bind(&Employee::set_address, std::ref(*employee), new_value)}
};

为什么绑定函数不适用于解引用迭代器？

Why bind function does not work with dereferencing iterator?

c++

iterator