Question

Thanks for looking at my question in advanced. It may be quite a simple one!

I have a menu where the user can select which file they wish to run through the system.

The code below is what my menu options do:

int menuLoop = 1;
int userChoice;
std::string getInput;

while(menuLoop == 1)
{
    std::cout << "Menu\n\n" 
         << "1. 20 names\n"
         << "2. 100 names\n"
         << "3. 500 names\n"
         << "4. 1000 names\n"
         << "5. 10,000 names\n"
         << "6. 50,000 names\n\n";
    std::cin >> userChoice;

    std::string getContent;

    if(userChoice == 1)
    {
        std::cout << "\n20 names\n"; 
        std::ifstream openFile("20.txt");
    }
    else if(userChoice == 2)
    {
        std::cout << "\n100 names\n"; 
        std::ifstream openFile("1C.txt");
    }
    else if(userChoice == 3)
    {
        std::cout << "\n500 names\n"; 
        std::ifstream openFile("5C.txt");
    }
    else if(userChoice == 4)
    {
        std::cout << "\n1000 names\n"; 
        std::ifstream openFile("1K.txt");
    }
    else if(userChoice == 5)
    {
        std::cout << "\n10,000 names\n"; 
        std::ifstream openFile("10K.txt");
    }
    else if(userChoice == 6)
    {
        std::cout << "\n50,000 names\n"; 
        std::ifstream openFile("50K.txt");
    }

The code that follows in the while loop deals with the values that are in the selected file, but the code is the same for each option. The next line is:

if(openFile.is_open())

Because of the way I have done it, it is saying “openFile” is undefined, which I completely understand but I was wondering whether anyone knows how I could get around?

Answer 1

Declare openFile just once earlier in the while loop like so:

std::ifstream openFile;

This gives you an std::ifstream that is not associated with any particular file. Then in each of your if statements use std::ifstream::open rather than the std::ifstream constructor:

openFile.open("20.txt");

Of course, make sure each one has the correct file name.

This way, the openFile object’s scope will be the while loop but you can open a different file depending on your condition.