c++ - C ++如何继续主直到用户选择退出选择

Question

int main()
{
    string selection;
    // print out selection menu
    selection = userOption();
    cout << selection << endl;

    //now perform web parser
    webparser(selection);    

    //now perform searchstring
    searchString(selection);
return 0;
}

以上是我的部分代码字符串 userOption() 是一个像这样打印出菜单的函数

货币

1. 美元/新加坡元
2. 欧元/美元
3. 输入您自己的货币对
4. 退出程序

我如何让 main 不退出，直到从 userOption 选择 4

Answer 1

一个简单的do-while：

int main()
{
  string exitstr("4");
  string selection;
  do {
    // print out selection menu
    selection = userOption();
    cout << selection << endl;
    if (selection == exitstr)
      break;
    //now perform web parser
    webparser(selection);    

    //now perform searchstring
    searchString(selection);
  } while (1);
return 0;
}

Answer 2

int main()
{
    string selection;
    while( (selection = userOption()) != "4")
    {
        cout << selection << endl;
        //now perform web parser
        webparser(selection);    
        //now perform searchstring
        searchString(selection);
    }
    return 0;
}

Answer 3

int main()
{
    for (;;)
    {
        string selection;
        // print out selection menu
        selection = userOption();
        cout << selection << endl;

        if (selection == "4") break;

        //now perform web parser
        webparser(selection);    

        //now perform searchstring
        searchString(selection);
    }
    return 0;
}

类似于 perreals 的答案。有很多方法可以编写“无限”循环，我认为在循环头（作为 this 或 by while(true)）中表达它会更好 - 当你开始阅读循环时，你会立即知道结束条件在里面的某个地方。