while循環C編碼錯誤

Question

這裏發生了什麼問題？我收到錯誤Use of undeclared identifier 'answer'

這裏是我的代碼：

 if (CalculatorChoice == 1) do { 
      int a; 
      int b; 
      int sum; 
      char answer; 

      printf ("You have choosen addition, please enter first number: "); 
      scanf("%d", &a); 
      printf ("Now please enter second number to addit: "); 
      scanf("%d", &b); 
      printf("The sum is: %d \n\n", sum = a+b); 

      printf("Do you want to go back to menupage? (y/n): "); 
      answer = getchar(); 
      getchar(); 
     } while(answer=='y'); 

Answer 1

if (CalculatorChoice == 1) 
    do { 
    /* ... */ 
    char answer; 

    /* ... */ 
    } while(answer=='y'); 

你聲明的變量answer內環形塊，但它是從while條件，這是外部訪問循環塊。

您可以將循環體外面的聲明來解決這個：

if (CalculatorChoice == 1) { 
    char answer; 
    do { 
    /* ... */ 
    } while(answer=='y'); 
} 

Answer 2

你的版本里面塊聲明的變量，是不是出塊的訪問

這段代碼改變位置

if (CalculatorChoice == 1) 
{ 
    char answer; 

    do { 
    int a; 
    int b; 
    int sum; 

    printf ("You have choosen addition, please enter first number: "); 
    scanf("%d", &a); 
    printf ("Now please enter second number to addit: "); 
    scanf("%d", &b); 
    printf("The sum is: %d \n\n", sum = a+b); 

    printf("Do you want to go back to menupage? (y/n): "); 
    answer = getchar(); 
    getchar(); 
    } while(answer=='y'); 
    }