Question

i am experiencing much trouble reading in files from input into an array struct. here is the code if someone can tell me what im doing wrong i can figure it out. the loop is supposed to be reading 2 strings, and 1 int, and skipping possible blank lines. but when i run it, it reads the first set and doesnt read nothing after that.

struct Instruments 
{
string model;
string maker;
int year;
};

int main()
{
int size;
Instruments data[20];
int i =0;

ifstream fin;
fin.open("input.txt");

for (i=0; i<20; i++)
{
 do{
getline(fin, data[size].model);
    getline (fin, data[size].maker);
fin >> data[size].year;

    size++;
 }
 while (data[size].model.length() > 0);
 }

fin.close();

for(int i=0;i<size; i++)
{
        cout << data[i].model << "model"<<endl;
        cout << data[i].maker << "maker" << endl;
        cout << data[i].year<< " year" << endl;
}
return 0;
}

Answer 1

There are multiple issues here:

1. Your first ‘for’ loop is using i as the loop counter but size as the array index.

2. After this call:

   fin >> data[size].year

   it will read to the end of the number and any whitespace that follows will form part of your next read, so if you are expecting to start the next record at the next line, do a blank getline() here too.

Aside from that.

1. Use vectors not arrays
2. Have a method to read from a stream into your struct, and if that succeeds, use push_back() to add it to your vector.

That doesn’t necessarily mean you have to loop until the read fails, it may be that you know in advance how many you wish to read. But you should still do it this way.