Need help with implementing input validation to data structure

Depressed (152)
I am in a bit of a pickle here trying to see how I can implement input validation with structure data types in a function. I am trying to make it so it accepts positive integers and no special characters.

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#include<iostream>
#include<iomanip>
#include<string>

using namespace std;


struct monthlyBudget
{
    double  housing = 580.00;
    double  utilities = 150.00;
    double  houseHoldExpenses = 65.00;
    double  transportation = 50.00;
    double  food = 250.00;
    double  medical = 30.00;
    double  insurance = 100.00;
    double  entertainment = 150.00;
    double  clothing = 75.00;
    double  miscellaneous = 50.00;
};

struct monthlySpent
{
    double  housing;
    double  utilities;
    double  houseHoldExpenses;
    double  transportation;
    double  food;
    double  medical;
    double  insurance;
    double  entertainment;
    double  clothing;
    double  miscellaneous;
};

void showData(monthlyBudget *);

void getExpenses(monthlySpent *, string);

void compareExpenses(monthlyBudget *, monthlySpent *, string);

int main()
{
    monthlyBudget monthly;
    monthlySpent spent;
    monthlySpent *stdPtr2 = nullptr;
    monthlyBudget *stdPtr = nullptr;
    stdPtr = &monthly;
    stdPtr2 = &spent;

    string months;

    showData(stdPtr);

    getExpenses(stdPtr2, months);

    compareExpenses(stdPtr, stdPtr2, months);

    return 0;
}

void showData(monthlyBudget *m)
{
    double total;

    cout << "Here is your monthly budget for YEAR 2020:\n" << endl;

        cout << "Housing " << setw(9) << "$" << m->housing << endl;
        cout << "Utilities " << setw(7) << "$" << m->utilities << endl;
        cout << "Household " << setw(7) << "$" << m->houseHoldExpenses << endl;
        cout << "Transportation " << setw(2) << "$" << m->transportation << endl;
        cout << "Food " << setw(12) << "$" << m->food << endl;
        cout << "Medical " << setw(9) << "$" << m->medical << endl;
        cout << "Insurance " << setw(7) << "$" << m->insurance << endl;
        cout << "Entertainment " << setw(3) << "$" << m->entertainment << endl;
        cout << "Clothing " << setw(8) << "$" << m->clothing << endl;
        cout << "Miscellaneous " << setw(3) << "$" << m->miscellaneous << endl;

        cout << "=================================================" << endl;

        total = m->housing + m->utilities + m->houseHoldExpenses + m->transportation + m->food + m->medical + m->insurance + m->entertainment + m->clothing + m->miscellaneous;

        cout << "Total budgeted " << setw(2) << "$" << total << endl;

        cout << "=================================================" << endl;

        cout << endl;
}

void getExpenses(monthlySpent *s, string months)
{
    cout << "Enter month of expenditure: ";
    cin >> months;

    cout << endl;

    cout << "Enter actual monthly expenditures for each budget category" << endl;

    cout << endl;

        cout << "Housing: " << setw(9) << "$";
        cin >> s->housing;
        cout << "Utilities: " << setw(7) << "$";
        cin >> s->utilities;
        cout << "Household: " << setw(7) << "$";
        cin >> s->houseHoldExpenses;
        cout << "Transportation: " << setw(2) << "$";
        cin >> s->transportation;
        cout << "Food: " << setw(12) << "$";
        cin >> s->food;
        cout << "Medical: " << setw(9) << "$";
        cin >> s->medical;
        cout << "Insurance: " << setw(7) << "$";
        cin >> s->insurance;
        cout << "Entertainment: " << setw(3) << "$";
        cin >> s->entertainment;
        cout << "Clothing: " << setw(8) << "$";
        cin >> s->clothing;
        cout << "Miscellaneous: " << setw(3) << "$";
        cin >> s->miscellaneous;

        cout << endl;
}

void compareExpenses(monthlyBudget *m, monthlySpent *s, string months)
{
    cout << "               Budgeted" << "      Spent" << "     Difference" << endl;
    cout << "======================================================" << endl;

    cout << "Housing " << setw(13) << m->housing << setw(12) << s->housing << endl;
    cout << "Utilities " << setw(11) << m->utilities << setw(12) << s->utilities << endl;
    cout << "Household " << setw(10) << m->houseHoldExpenses << setw(13) << s->houseHoldExpenses << endl;
    cout << "Transportation "<< setw(5) << m->transportation << setw(13) << s->transportation << endl;
    cout << "Food " << setw(16) << m->food << setw(12) << s->food << endl;
    cout << "Medical " << setw(12) << m->medical << setw(13) << s->medical << endl;
    cout << "Insurance" << setw(12) << m->insurance << setw(12) << s->insurance << endl;
    cout << "Entertainment " << setw(7) << m->entertainment << setw(12) << s->entertainment << endl;
    cout << "Clothing " << setw(11) << m->clothing << setw(13) << s->clothing << endl;
    cout << "Miscellaneous " << setw(6) << m->miscellaneous << setw(13) << s->miscellaneous<< endl;
}
Last edited on
Duthomhas (13282)
The first thing to do is recognize that:

  the user will always press ENTER after every requested input

This makes getting input easy: use getline() and get a string.

Once you have that string, try to convert it to the type you desire and perform any other checks you want on it, such as range bounds.

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#include <ciso646>
#include <iostream>
#include <optional>
#include <sstream>
#include <string>

template <typename T>
std::optional<T> string_to( const std::string & s )
{
  std::istringstream ss( s );
  T result;
  try
  {
    ss >> result >> std::ws;
    if (!ss.eof()) throw 1;
    return result;
  }
  catch (...)
  {
    return {};
  }
}

int ask_integer( int min, int max )
{
  std::string s;
  getline( std::cin, s );
  auto x = string_to<int>( s );
  if (!x or (*x < min) or (*x > max))
  {
    std::cerr << "That ain't yo age, foo!\n";
    exit( 1 );
  }
  return *x;
}

int main()
{
  std::cout << "What is your age? ";
  int age = ask_integer( 0, 120 );
  std::cout << "Good job! You are " << age << " years old!\n";
}

Hope this helps.


Ack! Gotta run! if I typoed something let me know.
mbozzi (3944)
If I typoed something let me know.

The use of throw for local control flow is always suspect.

Also, the operator>> is potentially user-provided. It may be an error to catch(...) and swallow arbitrary exceptions thrown from user code.

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template <typename T>
std::optional<T> string_to( const std::string & s )
{
  std::istringstream ss( s );
  T result;
  ss >> result >> std::ws;
  if (!ss.eof()) return std::nullopt; 
  else return result;
}
Last edited on
Duthomhas (13282)
Yeah... I was thinking those things as I wrote that version of my string_to<>() function...
What you posted is my canonical version.

Still not sure why I did that.




It was late... and... I have no excuse. /hangs head in shame
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