[英]Struct type “does not provide a subscript operator”
I am trying to read values from a file into an array of structs. 我试图从文件中读取值到结构数组。 However, I keep getting compiler errors that tell me that my struct, Books, does not provide a subscript operator and I am lost. 但是,我不断收到编译器错误,告诉我我的struct,Books,没有提供下标操作符,我迷路了。
The struct is contained in a header file while declaration of the array of structs is in main(). 结构包含在头文件中,而结构数组的声明在main()中。 Here is the (relevant) code from the functions.h header file: 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;
}
And here is the array of struct declaration in main along with how it is used: 这里是main中的struct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;
}
}
Once compiled, I get 10 error messages (one for each time I use array[position]) that state: error: type 'Books' does not provide a subscript operator 编译完成后,我收到10条错误消息(每次使用一个数组[position]时)状态: 错误:类型'Books'不提供下标运算符
There are too many problems in your code, you define the READ_INVENTORY
as a global function. 您的代码中存在太多问题,您将READ_INVENTORY
定义为全局函数。 So you might have received that there is an undefined reference to functions::READ_INVENTORY
. 所以你可能已经收到了functions::READ_INVENTORY
的未定义引用。 Another problem is you pass Books
instead of Books*
so you can't use the []
operator. 另一个问题是您传递Books
而不是Books*
因此您无法使用[]
运算符。
Change this 改变这个
void READ_INVENTORY(Books array, int max, int position)
{
to 至
void functions::READ_INVENTORY(Books* array, int max, int position)
{
Now that we have changed the parameter type, change this line 现在我们已经更改了参数类型,请更改此行
case 1: bookstore.READ_INVENTORY(booklist[choice], MAX_SIZE, size);
to 至
case 1: bookstore.READ_INVENTORY(booklist, MAX_SIZE, size);
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