如何从 1 个类访问其他类结构

Question

I'm a beginner and trying to learn coding. So please excuse if my question is stupid. I have these 2 classes and I want the class Store to have access a data from struct Stock in class Toys. I'm not sure how can I do this?

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

class Toys {
public:
    struct Stock
    {
        int x;
        Stock(int value)
            :x(value) {}
    };
};

class Store {
public:
    Toys myToy(int count) {
        _count = count;
    }
    Toys* myStore;
    //What do I need to do to bind a struct Stock from class Toy here?
private:
    int _count;
};

int main()
{
    Store myStore;
    int x;
    std::vector<Toys::Stock> stocks;
    std::cout << "Enter the availability for Water Gun.\n";
    std::cin >> x;
    for (int i = 0; i <= x; i++) {
        stocks.push_back(i);
        std::cout << stocks[i].x << std::endl;
    }
//Later I want to pull vector stocks from class Store here.
    return 0;
}

Answer 1

您可以将 Store 用作 Toys 的朋友类，这使您可以在 Store 类中使用 Toys 类的数据成员 试试吧！

Answer 2

Normally you'd have to add a friend declaration saying that you want to access private data from a particular class but since in your given example Stock is a struct and since you've used public access specifier inside Toys while declaring Stock , there is no need for the friend declaration here.

This means, you can create an instance of type Toys::Stock inside Store without having any friend declaration as shown below:

class Store {
public:
    
    Toys* myStore;
    
    Toys::Stock s1; // a data member named `s1` of type Toys::Stock
  
    Toys::Stock* ptr; //a data member named `ptr` of type Toys::Stock*
    int _count;
};