C：switch语句中的退出情况

Question

i just have a quick question regarding the switch case. can I do this? I can't get it to work. the program just says invalid 3 times when i type quit. excuse the pseudo code. oops i forgot to mention that the printf function looks like this before that part.

char choice;
printf("list, add, delete, write, quit\n");

do
{
scanf("%c", &choice);
//if (&choice== "quit"){exit(1);}

switch(choice)
    {
        case "list":
        case "add":
        case "delete":
        case "write":
        default:
            printf("Invalid\n");
            break;
        case "quit":
        exit (1);

    }while(&choice !="quit");

}

Answer 1

You can't compare strings like that. String comparison should be done with strcmp and its kin. In this case, you're comparing the addresses of the strings.

Answer 2

although you can't compare strings directly the way you want, there's a way you can use dictionaries and defines/enums to engage a switch (see what I did there):

enum choices { LIST, ADD, DELETE, WRITE, QUIT, INVALID };

int
getchoice(char *input)
{
    static struct choices {
        enum choices val;
        const char *string;
    } choices [] = {
        { LIST, "list" },
        { ADD, "add" },
        { DELETE, "delete" },
        { WRITE, "write" },
        { QUIT, "quit" },
        { -1, NULL }
    };
    int i;

    for (i = 0; choices[i].val != -1; i++)
        if (strcmp(input, choices[i].string) == 0)
            break;
    if (choices[i].val == -1)
        return INVALID;
    return (choices[i].val);
}

and then for your switch statement:

switch (getchoice(choice)) {
case LIST:
case ADD:
case WRITE:
case DELETE:
case INVALID:
default:
    printf("Invalid\n");
    break;
case QUIT:
    exit(1);
}

caveat emptor, as this hasn't been run through a compiler, but the general idea should be clear enough to adapt to your specific case(s).

Answer 3

另外，由于您在default情况下不使用break ，因此您将自动“跳入”默认情况（即使您输入的choice与“ list”，“ add”，“ delete”和“ write”相匹配） ）

Answer 4

To answer your question:

yes, you can call exit() anywhere, including inside a switch-case statement.

But that code has many issues, see my comment at the question itself.