How to understand C++ function/data structs?

Question

5. 'strToDouble' was not declared in this scope Lab1-3.cpp /Lab1-3/src line 65 C/C++ Problem

Answer 1

The first problem, as @SoronelHaetir pointed out, is that you were trying to assign title to variable which can only hold one character. Instead, you should use char array, char pointer, or even string object to contain your multi-letter value. In my code example below, I used char array with fixed size of 25, to store the title. Beware that you can store only up to 24 characters in it, because char arrays need special character which will denote the end of char array. Otherwise it would end up writing junk after your desired value. That special character is null-terminating character which is written like '\0'.

Using return; statement in your void displayBid(Info itemOne); function was completely unnecesary. While you can use return; to stop function from executing, you placed it at the end of function which was just about to end itself in normal way, but you forced it with no reason. Besides, you do not need any return; statements for functions which return void – nothing.

Then, fund and bidAmount are representing money value, which may or may not be of integer value, so you should consider float or double data types to store money value.

Next thing is your function Info getBid();. First, I have to say that naming may be a bit confusing. If you read the name of that function without seeing its actual code, how would you understand what it may do? For me, it sounded like it is about to get me information about a bid, while actually it is setting it up. Second, you could simplify code for entering values, in the way I did it in my code example. The way you tried to use different techniques for getting values from user input was a bit wrong. getline is member function which is used with istream objects. Your istream object is cin. In order to access that member function you shall write it as cin.getline(to be discussed);. That function only works with characters. Its first parameter accepts pointer to the first character (address of the first character) in sequence of characters.

Second parameter is of integer data type and specifies how much characters you want to be extracted from your input and stored in an argument which is in place of the first parameter. Beware not to write, for example, 25, because in char array you have to leave one place for '\0' character, which is automatically placed where it needs to be. getline member function has also default delimiter '\n', which denotes new line. It means that you can enter less characters than function can extract, because extraction will stop as soon as it reads that delimiter value from user input. Although, if you want your specific delimiter, getline member function has its overloaded version which third parameter is one where you enter desired delimiter as an argument. (Overloaded functions are basically functions with the same name, but different parameters. They provide same functionality with different implementation.)

Even if you had set up values for a bid, you never returned it from function. You correctly said that its return value is Info, but you did not return it. Actually, you again exited just before its normal exit. Instead, you should have written return itemOne; In my code example, I passed the variable created in int main(); function by reference, which means it is not a copy as usually, so I do not have to return it and assign to another variable of the same type to appropriately apply desired changes.

Finally, in the int main(); function, you could just declare int choice, without initializing it and use do-while loop in the way I did it. Also, switch statement provides defining what will happen if none of the cases are true, in the way that after all cases you write default:, and below it whatever you want to happen. In your code example, your function will continue executing even if user enters anything but 1, 2 except for 9 defined to stop its execution. In my code example, whatever user enters besides 1 and 2, including zero, function will exit. Well, except for new line.

And, let us discuss again the naming. Your data structure name has to directly imply what it is. Info does not do that. That name would actually be more appropriate for your void displayBid(Info itemOne); function to be called. In my code example, I renamed it to Bid.

#include <iostream>
using namespace std;

struct Bid
{
    char title[25];
    int vehicleID;
    double fund;
    double bidAmount;
};

void GetBid(Bid item)
{
    cout << "Title: " << item.title << endl;
    cout << "Fund: " << item.fund << endl;
    cout << "Vehicle: " << item.vehicleID << endl;
    cout << "Bid Amount: " << item.bidAmount << endl;
}

void SetBid(Bid & item)
{
    cout << "Enter title: ";
    cin >> item.title;

    cout << "Enter fund: ";
    cin >> item.fund;

    cout << "Enter vehicle ID: ";
    cin >> item.vehicleID;

    cout << "Enter amount: ";
    cin >> item.bidAmount;
}

int main()
{
    Bid item;
    int choice;

    do {
        cout << "Menu:" << endl;
        cout << "  1. Enter Bid" << endl;
        cout << "  2. Display Bid" << endl;
        cout << "  0. Exit" << endl;
        cout << "Enter choice: ";
        cin >> choice;

        switch (choice)
        {
            case 1:
                SetBid(item);
                break;
            case 2:
                GetBid(item);
                break;
            default:
                choice = 0;
                cout << "Goodbye." << endl;
                break;
        }
    } while (choice != 0);

    return 0;
}

Answer 2

The first (and biggest) problem is:

char title;

This allows you to store only a single character rather than an entire name (prefer std::string to char arrays).