Class 'FileIO' has an illegal zero-sized array; Multiple char strings as member data issue

Question

All I want is to store multiple char arrays as member data in the private field of my FileIO class. For some reason I can have one char array and it works fine, but I soon as I add a second, I get an the error stated in the title.

This code works fine:

class FileIO
{
private:
    char accNum[];
public:
    FileIO();
    ~FileIO();
    void WriteData(Account*);
    void WriteData(Person*);
    void ReadData(Account*);
};

This code throws an error:

class FileIO
{
private:
    char accNum[];
    char persName[];
public:
    FileIO();
    ~FileIO();
    void WriteData(Account*);
    void WriteData(Person*);
    void ReadData(Account*);
};

accNum[] is being used in the ReadData(Account*) function to store one character retrieved from a text file using getline(). Here's the code for that:

void FileIO::ReadData(Account * acc)
{
    ifstream accFile("accInfo.txt");
    accFile.getline(accNum, 100);
    cout << accNum << "\n";
    accFile.close();
}

There are more lines in the same text file that I want to store in separate char arrays, but as you can see, I can apparently only have one array as a member variable of the FileIO class. Why is this?

Answer 1

char accNum[]; is a zero sized array and is illegal in C++.

If you are going to be dealing with "strings" then you should scrap using c-style strings and use a std::string . Using a std::string your code would then become

class FileIO
{
private:
    std::string accNum;
public:
    FileIO();
    ~FileIO();
    void WriteData(Account*);
    void WriteData(Person*);
    void ReadData(Account*);
};

void FileIO::ReadData(Account * acc)
{
    ifstream accFile("accInfo.txt");
    getline(accFile, accNum);
    cout << accNum << "\n";
    accFile.close();
}