Question

Quick disclaimer, this is a contrived example meant to simulate an issue I am seeing in my homework problem. To that end, using strings is out of the question; I can only use char arrays as per the instructor 🙁

What I am trying to do is continuously read input from the keyboard and store it in a vector . The problem is, whatever data I add to the vector is lost as soon as the addData function ends (when I try to view it, I see \320\366\277_\377). I believe this is due to the fact I am using a vector<char*>, so the vector can only use the data for as long as the pointer exists. However, my code cannot compile if I change it to a vector<char>, as I get errors saying cannot convert char* to char.

So, how can I save a char array (not a single char) to a vector element? Or, is there perhaps a better approach to this that would avoid the problem altogether?

#include <iostream>
#include <cstring>
#include <vector>

using namespace std;
const int MAX_BUFFER_SIZE = 80;

// class declaration
class Example {
public:
    void getData ();
    void addData ( char * newData );
    void displayData ();

private:
    vector<char*> vec;
};

// main function
int main () {
    bool quitProg;
    int quit;
    quitProg = false;
    Example shoopDaWhoop; // buffers cannot overflow if you shoop da whoop
    while (!quitProg) {
        shoopDaWhoop.getData();
        shoopDaWhoop.displayData();
        cout << "Type 1 if you want to exit... ";
        cin >> quit;
        if (quit == 1) {
            quitProg = true;
        }
    }
    return 0;
}

void Example::getData () {
    char userInput [MAX_BUFFER_SIZE];

    cout << "Enter text: ";
    cin.get(userInput, MAX_BUFFER_SIZE - 1, '\n');
    if ( cin.fail() ) { // data is invalid
        // clear and reset input stream
        cin.clear(ios::goodbit);
        cin.ignore(INT_MAX,'\n');
        // alert user they entered bad data
        cout << "That was bad data!" << endl;
    }
    else {
        // data is good, pass it to addData
        addData( userInput );
    }
}

void Example::addData ( char * newData ) {
    vec.push_back(newData);
    cout << "You entered: " << vec.back() << endl;


}
void Example::displayData () {
    for (int i=0; i<vec.size(); i++) {
        cout << "Item " << i << ": " << vec[i] << endl;
    }

}

Answer 1

Use a std::vector<std::string>, that should “just work” with your existing code.

Since you cant do this with std::string (which would have been the proper way to use the language), the you a nested vector, like this:

std::vector<std::vector<char> > vex;  // notice the space between the '>' chars, older compilers may need it this way

Then in your addData function:

std::vector<char> tmp;

while(*newData)
   tmp.push_back(*newData++);

vec.push_back(tmp);