How could I use (char) to take sentences and output them(c++)? - c++

Question

While working on this project for my younger cousin, I encountered many difficulties. I was wondering if someone could help me use char to output complete sentences (or help me fix these bugs.) I'm a relatively new programmer (about 8 months). Here's my code/ what I have attempted. Most of the bugs cause the program to freeze once a sentence is imputed, or the files not responding when opened.
#include<iostream>
#include<fstream>
#include<cctype>
#include<iomanip>
class legoset
{
char setcatname[25];
char name[50];
char legoinclude[25];
char legotype[25];
public:
void create_category();
void show_category() const;
void modify();
void report() const;
int retacno() const;
};
void legoset::create_category()
{
std::cout << "Please enter a category name : \n";
std::cin >> setcatname;
//std::cin.getline(setcatname, 25);
std::cout << "Please enter your username! \n";
std::cin >> name;
std::cin.ignore();
std::cin.getline(name, 50);
std::cout << name << " , is it a vehicle or building (V/B)?\n";
std::cin >> legotype;
legotype[25] = toupper(legotype[25]);
std::cin.getline(legotype, 25);
std::cout << "\n Please enter the name of the lego set. \n";
std::cin >> legoinclude;
//std::cin.getline(legoinclude, 25);
std::cout << "\n\n Category Created Successfully!!!";
return;
}
void legoset::show_category() const
{
std::cout << "Category : \n" << setcatname;
std::cout << "Username Of Holder \n: " << name;
std::cout << " Lego type (B/V) : " << legotype;
std::cout << " Lego set (with details) : " << legoinclude;
return;
}
void legoset::modify()
{
std::cout << "Category : \n" << setcatname[25];
std::cout << "\nModify Holder's name : ";
std::cin.ignore();
std::cin.getline(name, 50);
std::cout << "\nModify A Building or vehicle class ( B/V ) : ";
std::cin >> legotype[25];
legotype[25] = toupper(legotype[25]);
std::cout << "\nModify Lego set (with details) : ";
std::cin >> legoinclude[25];
}
void legoset::report() const
{
std::cout << setcatname[25] << std::setw(10) << " " << name << std::setw(10) << " " << legotype[25] << std::setw(6) << legoinclude[25] << std::endl;
}
int legoset::retacno() const
{
return setcatname[25];
}
void write_legoset(); //function to write record in binary file
void display_sp(int); //function to display account details given by user
void modify_set(int); //function to modify record of file
void delete_set(int); //function to delete record of file
void display_all(); //function to display all account details
void intro(); //introductory screen function
int main()
{
char choice;
int num;
intro();
do
{
system("cls");
std::cout << "\n\n\n\tMAIN MENU";
std::cout << "\n\n\t01. New Category";
std::cout << "\n\n\t02. ADD A NEW SET";
std::cout << "\n\n\t03. ALL USERS HOLDER LIST";
std::cout << "\n\n\t04. DELETE A CATEGORY";
std::cout << "\n\n\t05. MODIFY A CATEGORY";
std::cout << "\n\n\t06. EXIT";
std::cout << "\n\n\tSelect Your Option (1-6) ";
std::cin >> choice;
system("cls");
switch (choice)
{
case '1':
write_legoset();
break;
case '2':
std::cout << "\n\n\tEnter The category Name : "; std::cin >> num;
display_sp(num);
break;
case '3':
display_all();
break;
case '4':
std::cout << "\n\n\tEnter The Category Name : "; std::cin >> num;
delete_set(num);
break;
case '5':
std::cout << "\n\n\tEnter The Category Name : "; std::cin >> num;
modify_set(num);
break;
case '6':
std::cout << "\n\n\tThanks for using lego managemnt system!";
std::exit;
break;
default: std::cout << "\a";
}
std::cin.ignore();
std::cin.get();
} while (choice != '6');
return 0;
}
//***************************************************************
// function to write in file
//****************************************************************
void write_legoset()
{
legoset lego;
std::ofstream outFile;
outFile.open("legoset.dat", std::ios::binary | std::ios::app);
lego.create_category();
outFile.write(reinterpret_cast<char *> (&lego), sizeof(legoset));
outFile.close();
}
//***************************************************************
// function to read specific record from file
//****************************************************************
void display_sp(int n)
{
legoset lego;
bool flag = false;
std::ifstream inFile;
inFile.open("legoset.dat", std::ios::binary);
if (!inFile)
{
std::cout << "File could not be open !! Press any Key...";
return;
}
std::cout << "\nLEGOSET DETAILS\n";
while (inFile.read(reinterpret_cast<char *> (&lego), sizeof(legoset)))
{
if (lego.retacno() == n)
{
lego.show_category();
flag = true;
}
}
inFile.close();
if (flag == false)
std::cout << "\n\nLego set does not exist in this file";
}
//***************************************************************
// function to modify record of file
//****************************************************************
void modify_set(int n)
{
bool found = false;
legoset lego;
std::fstream File;
File.open("legoset.dat", std::ios::binary | std::ios::in | std::ios::out);
if (!File)
{
std::cout << "File could not be open !! Press any Key...";
return;
}
while (!File.eof() && found == false)
{
File.read(reinterpret_cast<char *> (&lego), sizeof(legoset));
if (lego.retacno() == n)
{
lego.show_category();
std::cout << "\n\nPlease Enter The New Details For This Category." << std::endl;
lego.modify();
int pos = (-1)*static_cast<int>(sizeof(legoset));
File.seekp(pos, std::ios::cur);
File.write(reinterpret_cast<char *> (&lego), sizeof(legoset));
std::cout << "\n\n\t Category Updated!";
found = true;
}
}
File.close();
if (found == false)
std::cout << "\n\n Category Not Found ";
}
//***************************************************************
// function to delete record of file
//****************************************************************
void delete_set(int n)
{
legoset lego;
std::ifstream inFile;
std::ofstream outFile;
inFile.open("legoset.dat", std::ios::binary);
if (!inFile)
{
std::cout << "File could not be open !! Press any Key...";
return;
}
outFile.open("Temp.dat", std::ios::binary);
inFile.seekg(0, std::ios::beg);
while (inFile.read(reinterpret_cast<char *> (&lego), sizeof(legoset)))
{
if (lego.retacno() != n)
{
outFile.write(reinterpret_cast<char *> (&lego), sizeof(legoset));
}
}
inFile.close();
outFile.close();
remove("legoset.dat");
rename("Temp.dat", "legoset.dat");
std::cout << "\n\n\tCategory Deleted ..";
}
//***************************************************************
// function to display all accounts deposit list
//****************************************************************
void display_all()
{
legoset lego;
std::ifstream inFile;
inFile.open("legoset.dat", std::ios::binary);
if (!inFile)
{
std::cout << "File could not be open !! Press any Key...";
return;
}
std::cout << "\n\n\t\tUSER HOLDER LIST\n\n";
std::cout << "====================================================\n";
std::cout << "A/c no. NAME Type Balance\n";
std::cout << "====================================================\n";
while (inFile.read(reinterpret_cast<char *> (&lego), sizeof(legoset)))
{
lego.report();
}
inFile.close();
}
void intro()
{
std::cout << "\n\n\n\t LEGOSET";
std::cout << "\n\n\tMANAGEMENT";
std::cout << "\n\n\t SYSTEM";
std::cout << "\n\n\n\nMADE BY : Philippe Barry";
std::cin.get();
}
//***************************************************************
// END OF PROJECT
//***************************************************************

Answer 1

Note that array indices in C++ go from 0 to one less than the array size. Thus index 0 is the first element, index 1 is the second, etc. Thus if you declare a char array to be size 25, then accessing index 25 is past the end of the array and results in undefined behavior — your program may crash, freeze up, or literally anything else. Additionally, accessing index 24 would just give you the “null character” that comes after every string. If you’re sure that the input will be 24 characters long (and you shouldn’t be), then index 23 would contain the last character.
You really shouldn’t be using static-length char arrays in C++, anyway. Your current code, even if it worked most of the time with the char arrays, would fail when the input string was larger than the size of the array. Replace the types of all the char arrays with std::string, and the input function should work.
Furthermore, as Sam Varsavchik nicely put, don’t write an entire program at once. That makes it a nightmare to debug. Write your code in chunks — first write the input function, and a debug function that prints out the values of all the member variables. Debug that bit first, then go on to the rest.