Thread: Making a switch error proof

Code:

int exercises;

scanf("%d", &exercises);

    switch (exercises) {

            case 1: printf("1"); break;
            case 2: printf("2"); break;
            case 3: printf("3"); break;
            case 4: printf("4"); break;
            case 5: printf("5"); break;
            default: printf("Invalid command.\n"); break;
        
        }
    }

With this code, if the user enters any number other than 1-5, it goes to the default.

But if the user enters a letter, the program will go crazy.

I know that since I'm scanning for only ints, it will only default ints and nothing else.

Any way I can get it to default other kinds of inputs?

Take a look at the return value of scanf()...

Code:

int exercises;

if (scanf("%d", &exercises) > 0) 
  {
  switch (exercises) {
    case 1: printf("1"); break;
    case 2: printf("2"); break;
    case 3: printf("3"); break;
    case 4: printf("4"); break;
    case 5: printf("5"); break;
    default: printf("Invalid command.\n"); break;
    }
 }
else
  printf("Only numbers from 1 to 5 are valid");

I like CommonTater's solution. But it still doesn't work quite right.

My program continuously loops.

Code:

int main(int argc, char** argv) {

int exercises;
    
while (1) {
    printf( "1. Option 1\n"
            "2. Option 2\n"
            "3. Option 3\n"
            "4. Option 4\n"
            "5. Quit\n"
            "Choose a case: ");

if (scanf("%d", &exercises) > 0)
  {
  switch (exercises) {
    case 1: printf("1\n"); break;
    case 2: printf("2\n"); break;
    case 3: printf("3\n"); break;
    case 4: printf("4\n"); break;
    case 5: exit(EXIT_SUCCESS); break;
    default: printf("Invalid command.\n"); break;
    }
 }
else
  printf("Only numbers from 1 to 5 are valid");
}
}

If the user doesn't enter an int, it will print "Only numbers from 1 to 5 are valid" and the options over and over again.

Originally Posted by never_lose

I like CommonTater's solution. But it still doesn't work quite right.

My program continuously loops.

That's because there's stuff in the input buffer you aren't clearing out....

Code:

int main(int argc, char** argv) {

int exercises;
    
while (1) {
    printf( "1. Option 1\n"
            "2. Option 2\n"
            "3. Option 3\n"
            "4. Option 4\n"
            "5. Quit\n"
            "Choose a case: ");

if (scanf("%d", &exercises) > 0)
  switch (exercises) {
    case 1: printf("1\n"); break;
    case 2: printf("2\n"); break;
    case 3: printf("3\n"); break;
    case 4: printf("4\n"); break;
    case 5: exit(EXIT_SUCCESS); break;
    default: printf("Invalid command.\n"); break;
    }
else
  { 
     printf("Only numbers from 1 to 5 are valid");
     while (getchar()); 
   }  
  }
}

Originally Posted by Salem

It's depressing to see so many senior posters getting this so horribly wrong

OK.... what's your solution?

Originally Posted by Salem

It's depressing to see so many senior posters getting this so horribly wrong

It's like Rumsfeld all over again. "There are things we know, we don't know. There are things we don't know we know."