Need help understanding passing file stream to a function using a Switch statement

[dinmatt]

I am brand new to trying to learn C++ and have signed up for a class to expand my knowledge in this area. The instructor has never taught a class before and sadly, 16 students have dropped the class. I'm still trying to hang in there but I cannot make sense of some of an assignment. I am determined to figure it out, but I need some help with a piece that I have spent hours trying to get working and cannot.

I want to pass a file stream to case statements in a switch statement and in turn, each case will call a function to do something with the file stream. I can get the file open in the first case, but in the second, if i try to process it, i don't know how to pass the stream / file I captured in the first case. This is what I have so far:

#include<iostream>
#include<iomanip>
#include<cmath>
#include<ctime>
#include<string>
#include <fstream>
#include <cstdlib>

using namespace std;



//declare our functions
int DisplayMenu(string dataFile);
bool openFileIn(fstream &, char *);
void showContents(fstream &);

//FUNCTIONS

bool openFileIn(fstream &file, char *name){

file.open(name, ios::in);
if (file.fail())
return false;
else
return true;
}

void showContents(fstream &file) {
char line[50];
while (file >> line) {
cout << line << endl;
}
}


int DisplayMenu(){
//display the main menu
int item;


//Show user for the name of the data file
cout << endl << endl << endl;
//cout << "Current Data File: " << dataFile << endl << endl;

cout << "***** MAIN MENU *****" << endl << endl;
cout << "(1) Select / create data file (.txt extension will be added automatically)" << endl;
cout << "(2) Display all numbers, total and average" << endl;
cout << "(3) Display all numbers sorted" << endl;
cout << "(4) Search for a number and display how many times it occurs" << endl;
cout << "(5) Display the largest number" << endl;
cout << "(6) Append a random number(s)" << endl;
cout << "(7) Exit the program" << endl;

cout << "Menu Choice: ";
cin >> item;
return item;
}



int main() {

bool done = false;
string Filepath = " ";
string UserEntry;
string filePrefix = "C:\\Users\\Diana\\Documents\\CSC125\\Project\\Reid_Project\\";
string fileSuffix = ".txt";
fstream dataFile;
char* sDataFile;


int choice = DisplayMenu();

switch(choice)
{
case 1:
cout << "Enter file name. Do not include extension: ";
cin >> UserEntry;
Filepath=filePrefix;
Filepath.append(UserEntry);
Filepath.append(fileSuffix);

//convert string to char*
sDataFile = (char*)malloc( sizeof( char ) *(Filepath.length() +1) );
strcpy( sDataFile, Filepath.c_str() );

//check if file is found. if not, create it
if (!openFileIn(dataFile,sDataFile))
{
cout << "No file found." << endl;
//CreateFile(sDataFile);
}
else
cout << "file found!" << endl;
showContents(dataFile); //this works
DisplayMenu();


// break;
case 2:
//check if file is open
if (!openFileIn(dataFile,sDataFile))
{
cout << "No file found.." << endl;
//CreateFile(sDataFile);
}
else
showContents(dataFile); //this does not work
DisplayMenu();

break;
case 3:

break;
case 4:

break;
default:
cout << "Invalid selection. Choose a number between 1 and 7." << endl;
break;
}


return 0;
}

[kooth]

A couple of things:

First, in main, put your DisplayMenu() call in a loop and take it out of the case statements.

Make sure you add all of the case statements; especially case 7, to exit.

You don't need to copy strings into character arrays. If you need to call a function that takes a char*, use the string classes .c_str() method.

The way you are passing the stream to showContents() is correct.