Manipulating strings from a file

[Xatasha]

Hi all, second to last assignment for the semester! Thanks guys for all your help so far. This week I'm struggling to rewrite my last program so it does all the same things, but rather than storing in a variable and losing the data after the program exits, we're learning how to save it all to a file. That part is easy. I've written a function that has the user input a string containing first and last name, then changes it to last then first name with a comma, then writing to the file. I also have a function that displays it.

Now I need to rewrite my other functions so that only the last name is displayed without changing the data saved to file, rearrange the names alphabetically by last name (this does change the saved data), have the user to input a name then display a message if its found or not, and lastly let the user input a name and remove it (again, changing the saved data). Basically, I have no idea what functions would allow me to do this. In the previous writes of this program I had everything working with arrays, then with vectors. For this current one, I'm trying without. So I guess my first big question is, can I use the file data to have functions that do those things, or do I need to have a vector or array to manipulate?

[fg109]

Depending on how you're saving your data (how does it look in the save file?), you might not need vectors or arrays.

You need to post your code so that people don't have to look for your old posts and figure out what you're doing.

EDIT: Here is an example of loading and saving to a file without using arrays/vectors. I haven't tested it, so it may not work properly.

#include <iostream>
#include <fstream>
#include <string>
#include <cstdio>
#include <sstream>

struct Person
{
    std::string first, last;
    unsigned int age;
    bool isMale;
};

bool searchPerson(std::string fileName, std::string fullName)
{
    std::string str;
    std::ifstream fin(fileName.c_str());
    while (getline(fin, str))
        if (str == fullName)
        {
            fin.close();
            return true;
        }
    fin.close();
    return false;
}

void savePerson(std::string fileName, Person p)
{
    std::string fullName;
    fullName = p.last + ", " + p.first;
    if (searchPerson(fileName, fullName)) //person exists in file
    {
        std::string str;
        std::string tempFileName = "temp_" + fileName;
        std::ifstream fin(fileName.c_str()); //read from old file
        std::ofstream fout(tempFileName.c_str()); //create temp file
        while (getline(fin, str))
        {
            if (str != fullName) //don't change anything that's not our Person
                fout << str << std::endl;
            else
            {
                fout << fullName << std::endl;
                fout << p.age << std::endl;
                if (p.isMale)
                    fout << "Male" << std::endl;
                else
                    fout << "Female" << std::endl;
                fout << std::endl;
                //ignore the next 3 lines
                getline(fin, str);
                getline(fin, str);
                getline(fin, str);
            }
        }
        fin.close();
        fout.close();
        remove(fileName.c_str()); //delete old file
        rename(tempFileName.c_str(), fileName.c_str()); //rename temp file
    }
    else //person doesn't exist in file
    {
        //add to the file
        std::ofstream fout(fileName.c_str(), std::ofstream::out | std::ofstream::app);
        fout << fullName << std::endl;
        fout << p.age << std::endl;
        if (p.isMale)
            fout << "Male" << std::endl;
        else
            fout << "Female" << std::endl;
        fout << std::endl;
        fout.close();
    }
};

bool loadPerson(std::string fileName, std::string fullName, Person &p)
{
    if (!searchPerson(fileName, fullName)) //person doesn't exist in file!
        return false;

    std::string str;
    std::ifstream fin(fileName.c_str());
    while (getline(fin, str))
    {
        if (str == fullName)
        {
            p.last = str.substr(0, str.find(','));
            p.first = str.substr(str.find(',') + 2);
            getline(fin, str);
            std::istringstream sin(str);
            sin >> p.age;
            getline(fin, str);
            p.isMale = (str == "Male");
            fin.close();
            return true;
        }
    }
    fin.close();
    return false; //it should never get to here
}

It's assuming that the save file looks like this:

Doe, Jane
40
Female

Doe, John
43
Male
 

You can also do sorting without arrays/vectors, but that's so much trouble I'd rather use them instead.