结构类型 "does not provide a subscript operator"

Question

我正在尝试将文件中的值读入结构数组。但是，我不断收到编译器错误，告诉我我的结构 Books 没有提供下标运算符，我迷路了。

结构包含在头文件中，而结构数组的声明在 main() 中。这是 functions.h 头文件中的（相关）代码：

#ifndef FUNCTIONS_H
#define FUNCTIONS_H
#include <iostream>
#include <string>
#include <fstream>
using namespace std;

struct Books
{
        int ISBN;
        string Author;
        string Publisher;
        int Quantity;
        double Price;
};


class functions
{
        public:
                void READ_INVENTORY(Books, int, int);

};


// Function definitions

void READ_INVENTORY(Books array, int max, int position)
{
        ifstream inputFile;
        inputFile.open("inventory.dat");

        inputFile >> array[position].ISBN;
        inputFile >> array[position].Author;
        inputFile >> array[position].Publisher;
        inputFile >> array[position].Quantity;
        inputFile >> array[position].Price;

        cout << "The following data was read from inventory.dat:\n\n"
             << "ISBN: " << array[position].ISBN << endl
             << "Author: " << array[position].Author << endl
             << "Publisher: " << array[position].Publisher << endl
             << "Quantity: " << array[position].Quantity << endl
             << "Price: " << array[position].Price << endl << endl;
}

下面是 main 中的结构声明数组及其使用方式：

#include <iostream>
#include <string>
#include <fstream>
#include "functions.h"
using namespace std;

int main()
{
        const int MAX_SIZE = 100;
        int size, choice;
        functions bookstore;
        Books booklist[MAX_SIZE];

        cout << "Select a choice\n\n";

            cin >> choice;

            size = choice;

            switch (choice)
            {
                    case 1: bookstore.READ_INVENTORY(booklist[choice], MAX_SIZE, size);
                            break;

             }
}

编译后，我收到 10 条错误消息（每次使用 array[position] 时一条），指出：error: type 'Books' does not provide a subscript operator

Answer 1

你的代码问题太多，你把READ_INVENTORY定义为一个全局函数。因此，您可能已经收到对 functions::READ_INVENTORY 的未定义引用。另一个问题是你传递 Books 而不是 Books* 所以你不能使用 [] 运算符。

改变这个

void READ_INVENTORY(Books array, int max, int position) 
{

到

void functions::READ_INVENTORY(Books* array, int max, int position)
{

现在我们已经改变了参数类型，改变这一行

case 1: bookstore.READ_INVENTORY(booklist[choice], MAX_SIZE, size);

到

case 1: bookstore.READ_INVENTORY(booklist, MAX_SIZE, size);

结构类型 "does not provide a subscript operator"

Struct type "does not provide a subscript operator"

c++

arrays

struct

header-files

subscript-operator