如何从主(C ）访问函数中的值

我肯定会首先建议您尝试一些较小的程序，如果您是在C 中定义功能的新程序。

您定义为函数getChoice(char, char, char, char, char)的返回类型的类型是char，但是函数中的所有返回值（NewBorder除外）均为类型int，它是不合适的。

实际上，从函数" getChoice"的名称来看，该功能只能返回用户的"选择"而不是进一步发展，并且应在其他地方进行进一步的说明。

当用户输入'q'时，getChoice中的返回0语句不会导致主函数退出，而仅导致getChoice函数返回int值0。

我还考虑了一个判断用户选择时的所有if-else语句。

在我根据您的程序编写的以下代码中，在主函数内执行了更多说明。

#include <iostream>
#include <cassert>
using namespace std;
//constants:
const int MIN_HEIGHT = 3;
const int MIN_WIDTH = 3;
const int MAX_HEIGHT = 20;
const int MAX_WIDTH = 60;
const char H = 'h';
const char W = 'w';
const char B = 'b';
const char F = 'f';
const char Q = 'q';
//prototypes:
void drawRectangle(int row, int col, char border, char fill);
void displayChoices();
char getChoice(char h, char w, char b, char f, char q);
int main()
{
    char border = '#', fill = '*', choice;
    int newHeight = 0;
    int newWidth = 0;
    char newBorder = (char)0;
    char newFill = (char)0;
    int height = 10, width = 10;
    cout << endl << "Welcome! n";
    while (true)
    {
        drawRectangle(height, width, border, fill);
        cout << endl << "Choose from the following: n";
        displayChoices();
        choice = getChoice(H, W, B, F, Q);
        //if height is changed, update height. If width is changed, update width of rect.
        //if border is changed, update rectangle border. If fill is changed, update rectangle fill
        switch (choice)
        {
        case Q:
                return 0;
        case H:
                cout << "Enter new height between " << MIN_HEIGHT << " and " << MAX_HEIGHT << ": n";
                cin >> newHeight;
                while ((newHeight < MIN_HEIGHT) || (newHeight > MAX_HEIGHT)) {
                    cout << "That number is not in range. Try again.n";
                    cout << "Enter a number between " << MIN_HEIGHT
                        << " and " << MAX_HEIGHT << ": ";
                    cin >> newHeight;
                }
                height = newHeight;
                break;
        case W:
                cout << "Enter new width  between " << MIN_WIDTH << " and " << MAX_WIDTH << ": n";
                cin >> newWidth;
                while ((newWidth < MIN_WIDTH) || (newWidth > MAX_WIDTH)) {
                    cout << "That number is not in range. Try again.n";
                    cout << "Enter a number between " << MIN_WIDTH
                        << " and " << MAX_WIDTH << ": ";
                    cin >> newWidth;
                } 
                width = newWidth;
                break;
        case B:
                cout << "Enter new border character: n";
                cin >> newBorder;
                border = newBorder;
                break;
        case F:
                cout << "Enter new fill character: n";
                cin >> newFill;
                fill = newFill;
                break;
        }
    }
    return 0;
}
//draws rectangle
void drawRectangle(int row, int col, char border, char fill)
{
    for (int i = 0; i < row; i++) {
        for (int j = 0; j < col; j++) {
            if ((i == 0) || (i == (row - 1)) || (j == 0) || (j == (col - 1))) {
                cout << border;
            }
            else {
                cout << fill;
            }
        }
        cout << endl;
    }
}
//diplays users choices between height, width
//border and quit
void displayChoices()
{
    cout << "h) Change the height.n";
    cout << "w) Change the width.n";
    cout << "b) Change the border character.n";
    cout << "f) Change the fill character.n";
    cout << "q) Quit program.n";
}
//takes users choice and asks for the new value or character 
char getChoice(char h, char w, char b, char f, char q) {
    char choice, newBorder, newFill;
    int newHeight, newWidth, count = 0;
    cin >> choice;
    while ((choice != h && choice != w && choice != b && choice != f && choice != q)) {
        cout << "Not a valid choice. Choose again.n";
        cin >> choice;
    }
    return choice;

}

使用"使用名称空间std"实际上也是一种不好的做法；声明，但这可能会减少初学者的很多麻烦，因此您现在不需要关心这一点。请记住，您应该在一段时间后摆脱它。