Question

How would I get this to work? I get the error code that the letters are not declared, also how do I get the function to quit when they press Q?

char getChoice(char* choice)
{
printf("\nEnter the R, P, S, or Q (for quit) ");
scanf("%c", choice);
switch(*choice){
   case R:
   printf("You picked Rock, ");
   break;
   case P:
   printf("You picked Paper, ");
   break;
   case S:
   printf("You picked Scissors, ");
   break;
   case Q:

   default:
   printf("Error: Invalid choice, try again.");
   break; 
   }

 return *choice;
 }

Answer 1

First put the letters after case between '.
Second: modify que 'Q' case like this:
Change switch(*choice) to switch(choice). scanf wants a pointer and choice is already a pointer.

char getChoice(char* choice)
{
   ...
   case 'Q':
     return 0;
     break;

   default:
     printf("Error: Invalid choice, try again.");
     break;
}

Depending on how you call GetChoice you might return another value than 0.

There may be more issues depending on how you call getChoice.

Answer 2

You can edit your case statement like this;

switch(*choice)
{
   case 'R':
   printf("You picked Rock, ");
   break;
   case 'P':
   printf("You picked Paper, ");
   break;
   case 'S':
   printf("You picked Scissors, ");
   break;
   case 'Q':

   default:
   printf("Error: Invalid choice, try again.");
   break; 
}

Hope this helps.

Answer 3

这是一个彻底改进的get_choice：

#include <stdlib.h>  // for exit

char get_choice() {
    char choice;
    while (1) {
        printf("\nEnter the R, P, S, or Q (for quit) ");
        if (scanf("%c", &choice) != 1) {
            printf("Error reading a character!\n");
            exit(1);
        }

        switch(choice){
        case 'r':
            printf("You picked Rock, ");
            goto exit;
        case 'p':
            printf("You picked Paper, ");
            goto exit;
        case 's':
            printf("You picked Scissors, ");
            goto exit;
        case 'q':
            exit(0);
        default:
            printf("Error: Invalid choice, try again.");
            break;
        }
    }

exit:
    return choice;
}

（并且exit位于<stdlib.h>）

首先，现在您不需要传递指向char的指针来保存选择;它是在函数内部完成的。其次，我们对case标签使用字符常量 - 小写，因为这可能是用户宁愿写的东西。我们循环直到给出一个合适的值;如果给出，我们会使用exit跳转到goto标签。我们还检查scanf的返回值，如果没有字符可以读取（文件结束？），就会挽救

How can I make this switch statement work? Also how would I get the program to quit out when they enter Q?

3 个答案: