Question

I’m trying to get my program to loop through the file, taking in a load of information each time. However, at the moment after 2 correctly inputted lines it always goes to default, no matter what the contents of the file. Originally it was an eof while loop but I changed it to a for loop to try and fix it. Here’s my code:

ifstream furniture;
furniture.open("h://furniture.txt");


for(int i=0;i<=count;i++)
{
    type=0;
    furniture>>type>>name>>number>>material>>colour>>mattress;

    switch (type)
    {
    case 1:
        {
            Item* item= new Bed(number, name, material, colour, mattress);
            cout<<"working, new bed"<<endl;
            v.push_back(item);
            cout<<"working pushback"<<endl;
            count++;

            break;
        }
    case 2:
        {
            Item* item= new Sofa(number, name, material, colour);
            cout<<"working, new sofa"<<endl;
            v.push_back (item);
            cout<<"working pushback"<<endl;
            count++;

            break;
        }
    case 3:
        {
            Item* item= new Table(number, name, material, colour);
            cout<<"working, new table"<<endl;
            v.push_back(item);
            cout<<"working pushback"<<endl;
            count++;

            break;
        }
    default:
        {
            cout<<"Invalid input"<<endl;
            type=0;
            break;
        }
    }
}

I have tried a series of different solutions but nothing seems to have solved the problem.
Any help would be greatly appreciated.

Answer 1

ifstream‘s operator>> does not change the variable if the read fails, so type remains 0, thus the default branch is called. It seems like your file has a formatting error that makes the read fail.

Based on your comment, that you might not have all values in the file all the time, here is what you could do:

The best way would be to use getline() to read a full line, then use stringstream to extract the values from the line, handling the optional values in the process:

string line;
getline(furniture, line);
stringstream ss(line);
ss>>type>>name>>number>>material>>colour>>mattress;

If you provide default values to all those variables, they will keep the default if the line is ill-formatted or does not contain all of them.

The advantage of using getline() here is that the extraction via op>> does not mess up subsequent lines if there is a problem with the current line.