Here is a common stencil for processing menus:
bool invalid_selection = true;
while (invalid_selection)
{
// Output the menu with choices
// ...
char choice;
std::cin >> choice;
choice = std::toupper(choice);
switch (choice)
{
case 'A':
do_something;
break;
// ... other choices ...
default:
std::cout << "Invalid choice.";
}
if (choice == quit_character)
{
break; // exit out of the loop
}
}
There are many other alternatives. For example, one is a do-while loop.
If you don’t know about switch, use your if-else-if ladder. The final else clause is equivalent to the default case.
EDIT: It’d be even better to use a std::string as a buffer to prevent receiving multiple errors from this if the user inputs more than one char.
The best way to handle this would probably be a simple do… while nested switch statement:
#include <string>
bool repeat = true;
do {
std::string buffer;
cout << "Which plan do you want to use?" << endl;
cin >> buffer;
// check if the user entered only one character
if (buffer.length() > 1) {
cout << "Invalid Input" << endl;
continue;
}
plan = buffer[0];
switch(plan) {
case 'A':
// do things
repeat = false;
break;
case 'B':
// do things
repeat = false;
break;
case 'C':
// do things
repeat = false;
break;
default:
cout << "Invalid input, please try again." << endl;
break;
} while (repeat);
This keeps asking the user for which plan they want to use, until you receive valid input.
Note: OP did not want a complete refactoring of his code. So this is the minimal-intervention solution.
Edit your if statements to:
if(plan=='A'){
//...
} else if(plan=='B'){
//...
} else if(plan=='C'){
//...
} else {
//handle the error here.
cout << "Wrong input" << endl;
}