How to check if std::cin has failed - c++

Question

I am making a game and at the start, the player needs to assign points to different categories of their character (like Fallout's SPECIAL). Player input is currently read using std::cin. If the player inputs a letter instead of a number, std::cin will fail and crash the entire game.
I have attempted to check for failure with std::cin.fail() but no luck.
The relevant code which reads player input can be found below:
for(int i = 0; i < 5; i++) {
switch(i) {
case 0:
cout <<"\n\nStrength (How strong you are)";
cout <<"\nHow many points (you have " << total_SKILL_points << " left): ";
std::cin >>Strength;
if(std::cin.fail()) {
std::cin.clear();
cout <<"\n\nPlease enter a number!";
i--;
break;
}
total_SKILL_points = total_SKILL_points - Strength;
break;
// keeps going, that's why no closing } for switch or for loop.
Is there any proper way to check if a letter has been passed to std::cin?

Answer 1

You can clear the error flags and ignore the rest of the line if you get bad input.
#include <iostream>
#include <limits>
#include <list>
#include <string>
int main() {
int total_SKILL_points = 100;
int Strength;
while(true) {
std::cout << "\n\nStrength (How strong you are)\n"
"How many points (you have " << total_SKILL_points << " left): ";
if(std::cin >> Strength) { // check that cin is in a good state after extraction
// success
break;
} else {
// failure
if(std::cin.eof()) {
std::cout << "user aborted\n";
return 1;
}
std::cout << "\n\nPlease enter a number!";
// clear error flags
std::cin.clear();
// ignore rest of line
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}
}
std::cout << Strength << "\n";
}

Answer 2

I think try and catch is a good option here. You could do something like:
for (int i = 0; i < 5; i++){
switch(i){
case 0:
std::cout <<"\n\nStrength (How strong you are)";
std::cout <<"\nHow many points (you have " << total_SKILL_points << " left): ";
std::cin >>Strength;
int intStrength;
try{
intStrength = std::stoi(Strength);
}
catch(std::invalid_argument const &e){
std::cout <<"\n\nPlease enter a number!" << std::endl;
i--;
break;
}
total_SKILL_points = total_SKILL_points - intStrength;
break;

Answer 3

I have used the method that Peter gave. Thanks for the help.
Peter's answer for those skimming this post:
Using std::cin.fail() doesn't work in your case because the stream itself is not in an error state. std::cin >> Strength has stopped reading because of invalid input and left the invalid input in the stream to be encountered on the next read operation - but it does NOT put the stream itself in an error state. Instead of using std::cin >> Strength, read a line of input using
std::getline(std::cin, astring)
where a string is of type std::string and parse the string to check if it has required input or other data.
Note: don't mix use of std::getline() with >> on the same stream.