Possible to loop through an array structure in C++ - c++

Question

Apologize ahead of time if this may have been answered previously. Didn't find anything (or wasn't using the correct search terms). Regardless, There is a specific part of my code I wanted to know if I could step through with a loop. I went ahead and added the code below. Two sections that I feel could probably be cleaned up is the request for user input for how much was spent on various budget categories. I had plan to use a for loop, but couldn't figure how to assign values to various elements of the MonthlyBudget structure "currentMonthlyBudget" (i.e. currentMonthlyBudget.housing, currentMonthlyBudget.utilities, etc). It would have worked for the expenseCategories[], but I could find how (or if it is possible) to do it for the structure. Any assistance would be appreciated. Thanks in advance.
/* Exercise_10.cpp Monthly Budget Calculation*/
#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
using namespace std;
struct MonthlyBudget
{
double housing; //Housing
double utilities; //Utilities
double householdExpense; //Household Expense
double transportation; //Transportation
double food; //Food
double medical; //Medical
double insurance; //Insurance
double entertainment; //Entertainment
double clothing; //Clothing
double misc; //Miscellaneous
};
int main()
{
//Array of Monthly Budget Values
double defaultMonthlyBudget[10] = { 500.00, 150.00, 65.00,
50.00, 250.00, 30.00,
100.00, 150.00, 75.00,
50.00 };
//Array of Expense Categories
string expenseCategories[10] = { "Housing Accomodations", "Utilities", "Household Expenses",
"Transporation", "Food", "Medical Expenses", "Insurance",
"Entertainment", "Clothing", "Miscellaneous Expenses" };
//Array to hold the over budget and under budget values
double actualBudget[10] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
//Accumulator for actual budget
double sum = 0.00;
//Loop counter
int index;
//Final Total Budget
double calculatedTotalBudget = 0.00;
//Structure
MonthlyBudget currentMonthlyBudget;
cout << "Greetings. This program will determine if you are meeting your agreed upon budget." << endl;
cout << "I will ask you questions about your spending habits, and return a report to see how\n";
cout << "you did this month. Lets get started!\n\n\n";
cout << "\nPlease type in how much was spent this month for " << expenseCategories[0] << ": ";
cin >> currentMonthlyBudget.housing;
cout << "\nPlease type in how much was spent this month for " << expenseCategories[1] << ": ";
cin >> currentMonthlyBudget.utilities;
cout << "\nPlease type in how much was spent this month for " << expenseCategories[2] << ": ";
cin >> currentMonthlyBudget.householdExpense;
cout << "\nPlease type in how much was spent this month for " << expenseCategories[3] << ": ";
cin >> currentMonthlyBudget.transportation;
cout << "\nPlease type in how much was spent this month for " << expenseCategories[4] << ": ";
cin >> currentMonthlyBudget.food;
cout << "\nPlease type in how much was spent this month for " << expenseCategories[5] << ": ";
cin >> currentMonthlyBudget.medical;
cout << "\nPlease type in how much was spent this month for " << expenseCategories[6] << ": ";
cin >> currentMonthlyBudget.insurance;
cout << "\nPlease type in how much was spent this month for " << expenseCategories[7] << ": ";
cin >> currentMonthlyBudget.entertainment;
cout << "\nPlease type in how much was spent this month for " << expenseCategories[8] << ": ";
cin >> currentMonthlyBudget.clothing;
cout << "\nPlease type in how much was spent this month for " << expenseCategories[9] << ": ";
cin >> currentMonthlyBudget.misc;
cout << "\n\n\n";
//Compare inputted values to those of the predetermine budget
actualBudget[0] = (defaultMonthlyBudget[0] - currentMonthlyBudget.housing);
actualBudget[1] = (defaultMonthlyBudget[1] - currentMonthlyBudget.utilities);
actualBudget[2] = (defaultMonthlyBudget[2] - currentMonthlyBudget.householdExpense);
actualBudget[3] = (defaultMonthlyBudget[3] - currentMonthlyBudget.transportation);
actualBudget[4] = (defaultMonthlyBudget[4] - currentMonthlyBudget.food);
actualBudget[5] = (defaultMonthlyBudget[5] - currentMonthlyBudget.medical);
actualBudget[6] = (defaultMonthlyBudget[6] - currentMonthlyBudget.insurance);
actualBudget[7] = (defaultMonthlyBudget[7] - currentMonthlyBudget.entertainment);
actualBudget[8] = (defaultMonthlyBudget[8] - currentMonthlyBudget.clothing);
actualBudget[9] = (defaultMonthlyBudget[9] - currentMonthlyBudget.misc);
//TEST
/*for (index = 0; index < 10; index++)
{
cout << actualBudget[index] << "\n";
}*/
//Add up actualBudget
for (index = 0; index < 10; index++)
{
sum += actualBudget[index];
}
//Assign value to Calculated Total Budget
calculatedTotalBudget = (1420.00 - sum);
//Loop to display what categories we went over, under, & met our budget
for (index = 0; index < 10; index++)
{
if (actualBudget[index] < 0.00)
{
cout << "For the category of " << expenseCategories[index] << ", you went over your budget by $" << abs(actualBudget[index]) << ".\n";
}
else if (actualBudget[index] > 0.00)
{
cout << "For the category of " << expenseCategories[index] << ", you came in under your budget by $" << abs(actualBudget[index]) << ".\n";
}
else
{
cout << "For the category of " << expenseCategories[index] << ", you met your budget exactly.\n";
}
}
//Provide information to the user if the grand total went over, under, or met our total budget
if (calculatedTotalBudget > 1420.00)
{
cout << "This month's total expenditure was $" << calculatedTotalBudget << ". You were over budget by $" << (calculatedTotalBudget - 1420.00) << ".\n";
}
else if (calculatedTotalBudget < 1420.00)
{
cout << "This month's total expenditure was $" << calculatedTotalBudget << ". You were under budget by $" << abs(1420.00 - calculatedTotalBudget) << ".\n";
}
else
{
cout << "This month's total expenditure was $" << calculatedTotalBudget << ". You met your budget exactly.\n";
}
}

Answer 1

A clean solution could be to just hold a vector of categories and references to the values they map to
//Array of Expense Categories
std::vector<std::pair<string, double&>> expenseCategories = {
{ "Housing Accomodations", currentMonthlyBudget.housing },
{ "Utilities", currentMonthlyBudget.utilities },
{ "Household Expenses", currentMonthlyBudget.householdExpense },
{ "Transporation", currentMonthlyBudget.transportation },
{ "Food", currentMonthlyBudget.food },
{ "Medical Expenses", currentMonthlyBudget.medical },
{ "Insurance", currentMonthlyBudget.insurance },
{ "Entertainment", currentMonthlyBudget.entertainment },
{ "Clothing", currentMonthlyBudget.clothing },
{ "Miscellaneous Expenses", currentMonthlyBudget.misc }
};
Any loop will then just use either the category description or the value it maps to
for (auto& category : expenseCategories) {
cout << "\nPlease type in how much was spent this month for " << category.first << ": ";
cin >> category.second;
}
Live Example
The solution above has the advantage that you can reorganize your fields as you wish and just update the references involved.
For a simple data structure like the one you have you might as well have referred to its fields as in a simple array (i.e. by getting the pointer to the first element and then iterating over those).

Answer 2

If you really want to make a for loop from the MonthlyBudget input, you can do it by creating an array of a simple struct:
struct BudgetInputInfo {
std::string message;
double& targetValue;
}
Just create a static array of this, and you can write your for loop based on that array.
You can even add a method to this struct which displays the message, and sets targetValue.
Later, when you have other members than doubles, you can change this into a template.
But I think this won't result in the most readable code, you won't get a real benefit from the for loop, unless you want to be able to change the list it's based on runtime.
If your list is fixed like in the example, creating a function which prints out the message and reads the input would be more readable:
void readInput(std::string targetName, double& target) {
cout << "Please type in how much was spent this month for " << targetName << ": ";
cin >> target;
cout << endl;
}
With this, you would only have a few relatively short readInput calls.
You can even make a function which reads every member of a MonhtlyBudget:
void readMonhtlyBudget(MonthlyBudget& m) {
readInput("Housing Accomodations", m.housing);
// ...
}
Also, I would change your 10 element arrays to be instances of MonthlyBudgets. It's more clear, and you can even keep your current initializer syntax if you are using C++11:
MonthlyBudget defaultBudget = { 500.00, 150.00, 65.00,
50.00, 250.00, 30.00,
100.00, 150.00, 75.00,
50.00 };
And move the difference calculation code into a separate method, preferrable operator-:
MonthlyBudget operator-(MonthlyBudget const& a, MonthlyBudget const& b) {
MonthlyBudget result;
result.housing = a.housing - b.housing;
// ...
return result;
}
With these changes, you can just write:
actualBudget = defaultBudget - currentMonthlyBudget;