C 中循环中的 if 语句被跳过

在函数验证中，我有一个名为“size”的循环，它与“foodSelect”中的第三个循环相同，只是由于某种原因它的工作方式不同。它不会先提示我输入，而是直接进入其中的 if 并询问What size (L - Large, M - Medium, S - Small): Please enter S, M, or L only:。它首先显示错误，然后再次提示我输入。有点奇怪。

来源（因为很长）：http://pastebin.com/raw.php?i=KxrMAXaU http://pastebin.com/raw.php?i=KxrMAXaU

或来源在这里：

#include <stdio.h>
#include <string.h>

void menu();
void question (char choice[]);
void output(char *foodChoice, char *foodSelect, char *foodSize, int *foodOrderNum, float *foodSubtotal);
int verify(char *choice, char *foodChoice);

void menu() {
/*
printf("\n");
*/
    printf("\nWelcome to Sunny FISH & CHIPS!\n\n");
    printf("########     Fish :     Haddock(K) Large(L) | $5.00\n");
    printf("# FOOD #                Halibut(T) Large(L) | $4.00\n");
    printf("########     Chips:     Cut(C)     Large(L) | $2.00\n");
    printf("                        Ring(R)    Large(L) | $3.00\n");
    printf("                                            | \n");
    printf("##########   Soft Drinks(S)        Large(L) | $2.00\n");
    printf("# DRINKS #   Coffee(C)             Large(L) | $1.75\n");
    printf("##########   Tea(T)                Large(L) | $1.50\n");
    printf("---------------------------------------------\n");
    printf("Note: Medium price: 80%% of large.\n");
    printf("       Small price: 60%% of large.\n");
    printf("TAX is 10%%.\n");
    printf("More than 5 fish, 10%% discount on drink.\n");
    printf("Every 10 fish purchased, get 1 free softdrink.\n");
    printf("  - size of drink is according to size of fish\n");
    printf("----------------------------------------------\n\n");
}

int verify(char *choice, char *foodChoice) 
{
    int answer, rc = -1;
    if (choice == "order") 
    {
        do {
            answer = getchar();
            if (answer == 'Y' || answer == 'y')
            { rc = 1; }
            else if (answer == 'N' || answer == 'n')
            { rc = 0; }
            if (rc == -1 && answer != -1) 
            {
                printf("Please enter y or n only: ");
                while (answer != -1 && answer != '\n')
                answer = getchar();
            } 
        } while (rc == -1 && answer != -1);
    }
    if (choice == "foodSelect") 
    {
        do {
            answer = getchar();

                if (foodChoice == "Fish")
                {
                    do {
                        answer = getchar();
                        if (answer == 'K' || answer == 'k')
                        { rc = 1; }
                        else if (answer == 'T' || answer == 't')
                        { rc = 0; }
                        if (rc == -1 && answer != -1) 
                        {
                            printf("Please enter K or T only: ");
                            while (answer != -1 && answer != '\n')
                            answer = getchar();
                        }
                    } while (rc == -1 && answer != -1);
                }
                if (foodChoice == "Chips")
                {
                    do {
                        answer = getchar();
                        if (answer == 'C' || answer == 'c')
                        { rc = 1; }
                        else if (answer == 'R' || answer == 'r')
                        { rc = 0; }
                        if (rc == -1 && answer != -1) 
                        {
                            printf("Please enter C or R only: ");
                            while (answer != -1 && answer != '\n')
                            answer = getchar();
                        } 
                    } while (rc == -1 && answer != -1);
                }
                if (foodChoice == "Drinks")
                {
                    do {
                        answer = getchar();
                        if (answer == 'S' || answer == 's')
                        { rc = 1; }
                        else if (answer == 'C' || answer == 'c')
                        { rc = 2; }
                        else if (answer == 'T' || answer == 'T')
                        { rc = 3; }
                        if (rc == -1 && answer != -1) 
                        {
                            printf("Please enter S, C, or T only: ");
                            while (answer != -1 && answer != '\n')
                            answer = getchar();
                        } 
                    } while (rc == -1 && answer != -1);
                }   
        } while (rc == -1 && answer != -1);
    }
    if (choice == "size") 
    {
        do {
            answer = getchar();
            if (answer == 'S' || answer == 's')
            { rc = 1; }
            else if (answer == 'M' || answer == 'm')
            { rc = 2; }
            else if (answer == 'L' || answer == 'l')
            { rc = 3; }
            if (rc == -1 && answer != -1) 
            {
                printf("Please enter S, M, or L only: ");
                while (answer != -1 && answer != '\n')
                answer = getchar();
            } 
        } while (rc == -1 && answer != -1);
    }
}

void question (char *choice) {

    char *choiceYesNo;
    char *foodOptions;
    char *foodChoice;
    char *foodSelect;
    char *foodSize;
    int *foodOrderNum;
    float *foodSubtotal;

    switch (choice[0]) {
        case 'f':
            foodChoice = "Fish";
            foodOptions = "(K- Haddock, T- Halibut)";
            break;
        case 'c':
            foodChoice = "Chips";
            foodOptions = "(C- Cut, R- Ring)";
            break;
        case 'd':
            foodChoice = "Drinks";
            foodOptions = "(S- Softdrink, C- Coffee, T- Tea)";
            break;
    }

    printf("\nDo you order %s? (Y/N): ", foodChoice);
        verify("order", foodChoice);
    printf("%s choice %s: ", foodChoice, foodOptions);
        verify("foodSelect", foodChoice);
    printf("What size (L - Large, M - Medium, S - Small): ");
        verify("size", foodChoice);
    printf("How many orders do you want? (>=0): ");
        scanf("%d", &foodOrderNum);
    output(foodChoice, foodSelect, foodSize, foodOrderNum, foodSubtotal);
}

void output(char *foodChoice, char *foodSelect, char *foodSize, int *foodOrderNum, float *foodSubtotal) {

    printf("\nYou ordered %s: %c - SIZE: %c   amount ordered: %d, subtotal price: %.2lf\n\n", 
    foodChoice, foodSelect, foodSize, foodOrderNum, foodSubtotal);

}



int main() {

    //menu();

    question("drinks");


}

我不建议使用getchar()用于互动节目。您似乎无法处理在您输入的所有内容之后出现的换行符。使用fgets()反而。

To clarify the above, when you press something like YEnter, you have entered two characters into standard input. The first call to getchar(), will return 'Y', and the next call will return '\n' (the newline character). Your code does not expect this following newline character and may appear to "skip" calls to getchar(), when really it is returning more characters you entered.

如果你使用fgets()，然后你得到entire用户一次性键入的行，包括换行符。您（通常）不必担心输入缓冲区中等待的额外数据。