Switch default is not showing when it should-CodePudding

In my C program which is using switch I have problem with my int variable. My code is:

while(1) {
    printf("0. END\n1. TRANSLATE\n2. TEST FROM LESSON\n3. RANDOM"
            " WORDS TEST\n4. SHOW DICTIONARY\n5. ADD WORD\n"
            "6. DELETE WORD\nYOUR CHOICE: ");
    
    scanf("%d",&option);
    fflush(stdin);
    printf("\n");

    switch(option) {
        case 0: {
            exit(0);
            break;
        }
        
        case 1: {
            system("cls");
            translate();
            printf("\n");

            break;
        }

        case 2: {
            system("cls");
            lessons();
            printf("\n");
            
            break;
        }

        case 3: {
            randomFromLessons();
            printf("\n");
            
            break;
        }

        case 4: {
            system("cls");
            allWords();
            printf("\n");
            
            break;
        }

        case 5: {
            system("cls");
            addWord();

            break;
        }
        
        case 6: {
            system("cls");
            deleteWord();
            printf("\n");
            
            break;
        }
        
        default: {
            printf("---------------\n");
            printf("WRONG VALUE.\n");
            printf("---------------\n\n");
        }   
    }
    
}

When I type 'd' into option var. it shows default, which is what I want, BUT when I press number 1 which starts method named "translate()" and then get back into main menu and press 'd' again it gets me back into "translate()" instead of showing the default.

When I use char instead of int, there is no problem. So, what exactly is the problem? What keeps happening? What am I doing wrong? Isn't using char in switch the best option overall then?

CodePudding user response：

If you wish to allow text input, you should read the input as a string with fgets and then convert to integers as needed.

If you only wish to accept numbers, you should check the result of scanf to see if it succeeded - in this case it will return 1 when successful, in case it managed to read 1 parameter. If not successful, it won't overwrite option but keep the previous value - that's why you get the behavior you describe.

Furthermore fflush(stdin); is undefined behavior since fflush was never meant to be used on input streams. To just discard the line feed character from stdin you can add single getchar().

So you could fix the code into something like this:

int result;

while(1)
{
  result = scanf("%d",&option);
  getchar();
  if(result == 1)
    break;
  else
    printf("some error message\n");
}

switch(option)
...