Question

I am trying to validate user input. Here’s the code:

do{
        NSLog(@"Please select from the following options: D/ W/ T/ Q");
        res = scanf("%c", &s1);

        if(res ==0) {
            NSLog(@"Invalid entry.");
        }
    }while (res ==0); 

I want to improve the above code such that it will not allow the user to input anything (such as a number, a string, or any negative number) but only one single character (to be specific, only one of the option given in the prompt).

The current code doesn’t do that.

Answer 1

    boolean bValid = true;
    do {
        NSLog(@"Please select from the following options: D/ W/ T/ Q");
        res = scanf("%c", &s1);

        if(res == 'D' || res == 'W' || res == 'T' || res == 'Q'){
            bValid = false;
        }
        else{
            //Error message
        }
    } while (bValid == true);

You can use this code.
Just check it out.