.txt file to an array of structures in C++? - c++

Question

I have previously used C++, but I can definitely say I am not a pro. Not really even at coding in general. I'm trying, as much as it may not look like it. :/
My task is to create an array of structres of the type, "book_list".
the struct looks like this:
struct book_list
{
int bookNumber; string bookTitle; string bookAuthor;
string bookDescription; int bookMonth; int bookYear; int bookRating;
};
It's easy enough to create the array itself:
book_list myBookList[50];
Here's where I'm having trouble:
The program is intended to search for a .txt file. If it finds it, it will read into the array of structures all the data contained within the file. So, bookNumber with the .txt file's bookNumber, etc.
I have been looking up potential solutions all day, and I've looked into ideas such as ifstream, getline, using iterators, etc. My research has been as scattered as my brain, and I think I am a little stumped.
Please help, and if you need any further info, please let me know!
Thanks,
-Jon

Answer 1

You need to either read/parse each entry separately or read the entire file in then parse it. Since you're storing all the structs in memory anyway, the latter is probably fine if you don't want to bother with reading one at a time, but for educational purposes, you might want to try reading one at a time. Maybe separate by lines?
Then you need a way to parse the entries. There's no one way to do this, but the easiest is probably to use a JSON-formatted text file, mainly because there are libraries that can use it and tools that can help visualize it. JSON lets you represent dictionaries, arrays, strings, numbers, and booleans. You can either do this manually without much effort since you don't have anything fancy like nested structures, or you can use a library like this to parse JSON for you: https://github.com/DaveGamble/cJSON
(which is in C, will have to link with C++ if you want to use C++)

Answer 2

Assuming that the question may be formulated as:
can you give me a tiny programming example that can kickstart my exercise:
program p:
#include <iostream>
using namespace std;
int main() {
int num;
string buf;
while (true) {
cin >> num; if (cin.eof()) break;
cin >> buf; if (cin.eof()) break;
cout << "num is: " << num << " buf is: " << buf << endl;
}
}
text file t.txt
1
one
2
two
you can run
p < t.txt
and see that the output is what you probably expected.
Now of course change cin >> num; into cin >> booklist[0].bookNumber; etc. and your exercise will be on the right track.

Answer 3

Use <stdio.h> for FILE.
char *name;
FILE *file;
name = "database.txt";
file = fopen(name,"w+");
book_list myBookList[50];
While writing use this.
book_list newRecord;
newRecord.bookNumber = 0;
//other assignments
fseek(file,0,SEEK_END);
fwrite(&newRecord,sizeof(book_list),1,file);
fclose(file);
While reading use below.
file = fopen(name,"r+");
book_list record;
fseek(file,0,SEEK_SET);
int i=0;
while(true){
fread(&record,sizeof(book_list),1,file);
if(feof(file))
break;
myBookList[i].bookNumber = record.bookNumber;
//other assignments
i++;
}
fclose(file);
Note: I'm not sure this is working properly with string class.I have used this with char[SIZE] and strcpy. My suggestion is try this first with built-in types like int, float, char etc.