已经处理后如何检查cin？

Question

如果在检查另一个条件之前需要处理某些内容，检查输入的最佳方法是什么？代码片段：

#include <string>
#include <iostream>
#include <dirent.h>

bool has_suffix(const std::string &str, const std::string &suffix);

void get_path_get_exit(std::string &path_input);


int main()
{
    DIR *dir;
    struct dirent *ent;
    std::string path_input;
    std::getline(std::cin, path_input);



    const char *path = path_input.c_str();
    dir = opendir(path);
check:
    while ((dir) == NULL && !path_input.empty()){
        /* could not open directory */

        std::cout << "Whoops, that didn't work. Please enter a valid directory path." << std::endl << "-->";
        std::getline(std::cin, path_input);

        path = path_input.c_str();
        closedir(dir);
        dir = opendir(path);
    }
    if ((dir) != NULL) {

        unsigned int counter = 0;

        while ((ent = readdir (dir)) != NULL) {
            counter++;
        }
    /*check if the folder is empty*/ 
        if (counter == 0){
        /*how to surpass the goto statement?*/
            goto check;
        }
        std::string files[counter];


        closedir(dir);
        dir = opendir(path);
        counter = 0;
        while ((ent = readdir (dir)) != NULL) {

                files[counter] = ent->d_name;
                std::cout << "[" << counter+1 << "] " << files[counter] << std::endl;
                counter++;

        }
        closedir(dir);
    }
}

如您所见，我正在尝试检查 cin 输入，并在下一个 if 语句中尝试检查打开的目录是否为空。有没有更好的方法 "hop" 到顶部 'check' 的开头，以便再次进入 while 循环并再次使用更高的标准检查新输入？ Goto确实有用，但我觉得用起来有点惭愧

Answer 1

我可能没有完全理解你的问题，但我听起来你需要一个 do..while 循环

    const char *path = path_input.c_str();
    dir = opendir(path);
    do
    {
        while (//some criteria that aren't met){
           /* could not open directory */

           std::cout << "Whoops, that didn't work. Please enter a valid directory path." << std::endl << "-->";
           std::getline(std::cin, path_input);

           path = path_input.c_str();
           closedir(dir);
           dir = opendir(path);
       }
       if ((dir) != NULL) {

           unsigned int counter = 0;

           while ((ent = readdir (dir)) != NULL) {
               counter++;
           }
    /*check if the folder is empty*/
   } while(counter == 0)

Answer 2

提取一个检查条件的函数。这就是优秀的程序员在这种情况下所做的。

bool IsDirectoryValidForThisOperation(DIR *dir, std::string& failDesdcription)
{
    if (!dir) {
         failDesdcription = "Invalid directory";
         return false;
    }
    if (readdir(dir)) == NULL) {
         failDesdcription = "Directory is empty";
         return false;
    }
    // TODO: restore state of dir

    return true;
}

一个好的代码总是被恶意分解成小函数，因为：

更容易阅读
代码的许多部分可以在另一个上下文中重用
编写测试更容易
更容易调试
代码将自我记录

已经处理后如何检查cin？

How to check cin after already processed?

c++

validation

input

cin