How can reduce recursion within this function - c++

Question

can't figure out how to prevent recursion within this function, any suggestions or
recommendations? I've tried a couple of my own solutions but ran into the error of having
the program crash if wrong inputs and repeatedly entered.
Thanks in advance, DK.
static void CheckPlayerInput()
{
// gets the character entered (as a char)
cin >> input;
//check is actually a char
if (cin.fail())
{
//more recursion, could cause issues, could you find another way?
cout << "Invalid character, try again!" << endl;
CheckPlayerInput();
}
//converts char to upper case
input = toupper(input);
//check the input character
// maps the input keys to the grid reference
//calling the FillSquare method
switch (input)
{
case '1': FillSquare(0, 0); break; //top-left
case '2': FillSquare(0, 1); break; //top-centre
case '3': FillSquare(0, 2); break; //top-right
case '4': FillSquare(1, 0); break; //middle-left
case '5': FillSquare(1, 1); break; //middle-centre
case '6': FillSquare(1, 2); break; //middle-right
case '7': FillSquare(2, 0); break; //bottom-left
case '8': FillSquare(2, 1); break; //bottom-centre
case '9': FillSquare(2, 2); break; //bottom-right
//IF NOT ANY OF THE ABOVE
default:
{
//more recursion, could cause issues
//
cout << "Invalid character, try again!" << endl;
CheckPlayerInput();
}
break;
}
}

Answer 1

Use a do while loop instead
static void CheckPlayerInput()
{
bool invalid = false;
do
{
invalid = false;
// gets the character entered (as a char)
cin >> input;
...
default:
{
//more recursion, could cause issues
//
cout << "Invalid character, try again!" << endl;
invalid = true;
}
break;
}
}
while(invalid);
}
The while loop will repeat as long as the input is invalid

Answer 2

I guess there are many different ways to implement it.
The below might be my approach.
Note:
Filling the square feels like a dedicated task and should therefore be inside it's own function.
Maybe you should use non-static / non-global methods and instead use objects.
Your method CheckPlayerInput is not checking the input. Instead, it's processing it.
static bool
_fillSquare(char type)
{
switch (type)
{
case '1': FillSquare(0, 0); break; //top-left
case '2': FillSquare(0, 1); break; //top-centre
case '3': FillSquare(0, 2); break; //top-right
case '4': FillSquare(1, 0); break; //middle-left
case '5': FillSquare(1, 1); break; //middle-centre
case '6': FillSquare(1, 2); break; //middle-right
case '7': FillSquare(2, 0); break; //bottom-left
case '8': FillSquare(2, 1); break; //bottom-centre
case '9': FillSquare(2, 2); break; //bottom-right
default : return false;
}
return true;
}
// this method does not `check` the player input, but it
// `processes` it. The name should reflect that.
static void
processPlayerInput()
{
// try to retrieve and process input until
// a valid input was given
while (true)
{
cin >> input;
if (!cin.fail ())
continue;
input = toupper(input);
bool success = _fillSquare(input);
if (!success)
{
cout << "Invalid character, try again!" << endl;
continue;
}
return;
}
}