How do I get keyboard input for a const* char parameter? - c++

Question

I have an object that works with arrays of smaller objects. I am now creating a larger interface object that needs to collect input data and send it into a parameter of const* char. What code would I use to capture keyboard input of something like a 20 character title and be able to pass it into this parameter?
In Short:
How do you get keyboard input of a name and pass it into this:
void Insert(const char* t)
I am restricted to using the iostream, iomanip, cstring, cctype libraries
EDIT: You asked for the whole code, so here it is. All my input is having problems...
#include <iostream>
#include "store.h"
using namespace std;
void ShowMenu()
// Display the main program menu.
{
cout << "\n\t\t*** BOOKSTORE MENU ***";
cout << "\n\tA \tAdd a Book to Inventory";
cout << "\n\tF \tFind a book from Inventory";
cout << "\n\tS \tSell a book";
cout << "\n\tD \tDisplay the inventory list";
cout << "\n\tG \tGenre summary";
cout << "\n\tO \tSort inventory list";
cout << "\n\tM \tShow this Menu";
cout << "\n\tX \teXit Program";
}
char GetAChar(const char* promptString)
// Prompt the user and get a single character,
// discarding the Return character.
// Used in GetCommand.
{
char response;// the char to be returned
cout << promptString;// Prompt the user
cin >> response;// Get a char,
response = toupper(response);// and convert it to uppercase
cin.get();// Discard newline char from input.
return response;
}
char Legal(char c)
// Determine if a particular character, c, corresponds
// to a legal menu command. Returns 1 if legal, 0 if not.
// Used in GetCommand.
{
return((c == 'A') || (c == 'F') || (c == 'S') ||
(c == 'D') || (c == 'G') || (c == 'O') ||
(c == 'M') || (c == 'X'));
}
char GetCommand()
// Prompts the user for a menu command until a legal
// command character is entered. Return the command character.
// Calls GetAChar, Legal, ShowMenu.
{
char cmd = GetAChar("\n\n>");// Get a command character.
while (!Legal(cmd))// As long as it's not a legal command,
{// display menu and try again.
cout << "\nIllegal command, please try again . . .";
ShowMenu();
cmd = GetAChar("\n\n>");
}
return cmd;
}
void Add(Store s)
{
char* aTitle;
char aAuthor[21];
Genre aGenre = FICTION;
double aPrice = 10.00;
cout << "Enter title: ";
cin >> aTitle;
cout << "Enter author: ";
cin.getline(aAuthor, 20);
cout << aTitle << " " << "aAuthor\n";
s.Insert(aTitle, aAuthor, aGenre, aPrice);
}
void Find()
{
}
void Sell()
{
}
void Genre()
{
}
void Sort()
{
}
void Intro(Store s)
{
double amount;
cout << "*** Welcome to Bookstore Inventory Manager ***\n"
<< "Please input the starting money in the cash register: ";
cin >> amount;
s.SetCashRegister(amount);
}
int main()
{
Store mainStore;// Create and initialize a Store.
Intro(mainStore);//Display intro & set Cash Regsiter
ShowMenu();// Display the menu.
mainStore.Insert("A Clockwork Orange", "Anthony Burgess", SCIFI, 30.25);
mainStore.Insert("X-Factor", "Anthony Burgess", SCIFI, 30.25);
char command;// menu command entered by user
do
{
command = GetCommand();// Retrieve a command.
switch (command)
{
case 'A': Add(mainStore); break;
case 'F': Find(); break;
case 'S': Sell(); break;
case 'D': mainStore.DisplayStore(); break;
case 'G': Genre(); break;
case 'O': Sort(); break;
case 'M': ShowMenu(); break;
case 'X': break;
}
} while ((command != 'X'));
return 0;
}

Answer 1

Consider std::istream::getline(char *, std::streamsize).
But, be sure that you pass it a valid pointer to allocated memory! That is, use it like this:
char buffer[80];
std::cin.getline(buffer, sizeof buffer);
and not like this:
char *p;
std::cin.getline(p, 80); // Undefined behavior: using uninitialized variable
EDIT. You have this code:
char* aTitle;
...
cout << "Enter title: ";
cin >> aTitle;
This is a bug. You create a pointer called aTitle, and do not initialize it. That pointer now points at memory you do not own.
The >> operator writes data to the location pointed to by your pointer. Since your pointer does not point at anything you control, the >> will invoke undefined behavior when its writes through your pointer.
Lesson: make sure that you provide valid values for all of your pointers. (Broader lesson: never use pointers. (Okay, almost never.))
Immediately following, you have this code:
cout << "Enter author: ";
cin.getline(aAuthor, 20);
But, consider the input state. Your user just typed "Jaws", followed by ENTER. Your cin>>aTitle read "Jaws", and left "\n" in the input stream.
This istream::getline call reads up to the first newline, which is the newline that follows "Jaws"(!) and not the newline that follows "Peter Benchley"! So now, you have "Jaws" in aTitle (assuming you fix your previous bug), nothing in aAuthor, and "Peter Benchley\n" still in the input stream.
Lesson: Don't mix formatted input with getline. Use either one or the other consistently throughout your program.

Answer 2

Use getline to take a std::string input. And pass it to the function converting to a c-style string using member function c_str()

Answer 3

Use std::string and pass by reference.
You need a pointer to mutable data:
char * t; // Pointer to mutable data
OR
char* const t; // Constant pointer to mutable character.

Answer 4

Because of the weird restrictions (iostream is allowed, but not std::string), you might have a hard time finding your answer in a C++ text book. So here's some help:
char buffer[81];
std::cin >> buffer; // input some text (80 characters or less)
// A mutable character array can be implicitly converted
// to a const char* without casting.
Insert(buffer);