如何打印在c ++中具有第一和第二2类的对的向量？

Question

我有这样的东西，其中客户和订单是类：

  std::vector<std::pair<Client,Order>> pair;
    pair.push_back(std::make_pair(Client(2,"Anca"),Order(3,1)));
    pair.push_back(std::make_pair(Client(16,"Maria"),Order(1,3)));
    pair.push_back(std::make_pair(Client(29,"Alex"),Order(10,5)));

class Client{
private:
    int dateWhenOrderWasPlaced;
    std::string clientName;
public:
    Client(int date,std::string name){
        dateWhenOrderWasPlaced=date;
        clientName=name;
    }

class Order{
private:
    int amountPizza;
    int pizzaAge;
public:
    Order(int amPizza,int agePizza){
        amountPizza=amPizza;
        pizzaAge=agePizza;
    }

而且我不知道该如何打印。我已经尝试了很多方法：

void print(std::vector<std::pair<Client,Order>> pair){
    for(const auto& it : pair){
        std::cout << "First: "<<pair[it].first<< ", Second: " << pair[it].second <<std::endl;
    }
}

还有这个：

void print(std::vector<std::pair<Client,Order>> pair){
    for(const auto& it : pair){
        std::cout << "First: "<<it.first<< ", Second: " << it.second <<std::endl;
    }
}

并且在两种方式下我都有错误（第一位没有运算符[]和第二位，没有运算符<

Answer 1

您的第一次尝试不起作用，因为it是实际的配对，并且std::pair没有operator[]。您的第二次尝试是正确的方法，但是它没有用，因为您没有为operator<<或Client定义Order，例如

class Client
{
private:
    int dateWhenOrderWasPlaced;
    std::string clientName;

public:
    Client(int date, std::string name)
        : dateWhenOrderWasPlaced(date), clientName(name)
    {
    }

    friend std::ostream& operator<<(std:::ostream &os, const Client &c)
    {
        // print c.dateWhenOrderWasPlaced and c.clientName to os as needed...
        return os;
    }
};

class Order
{
private:
    int amountPizza;
    int pizzaAge;

public:
    Order(int amPizza, int agePizza)
        : amountPizza(amPizza), pizzaAge(agePizza)
    {
    }

    friend std::ostream& operator<<(std::ostream &os, const Order &o)
    {
        // print o.amountPizza and o.pizzaAge to os as needed...
        return os;
    }
};

void print(const std::vector<std::pair<Client,Order>> &pair)
{
    for(const auto& it : pair)
    {
        std::cout << "First: " << it.first << ", Second: " << it.second << std::endl;
    }
}