我试图通过编写一个简单的控制台应用程序来学习C ++。用户通过输入存储在变量中的数字来导航主菜单，然后switch语句用于确定要执行的操作。这很简单。 ：）
困扰我的问题是，当程序到达cin语句时，按回车而不输入数字不会退出＆＃34;声明，但只是碰到下一行。我想这是有道理的，但我怎么能让它如此紧迫的回归而没有先前的输入只是＆＃34;退出＆＃34;或者＆＃34;取消＆＃34; cin声明？
下面简要介绍了我的应用程序的样子：
int main()
{
int mainMenuSelector;
while(mainMenuSelector != 4){
cout << "--- MAIN MENU -----------------" << endl;
cout << "[1] First Option" << endl;
cout << "[2] Second Option" << endl;
cout << "[3] Third Option" << endl;
cout << "[4] Exit Application" << endl;
cout << "-------------------------------" << endl;
cout << "Selection: ";
cin >> mainMenuSelector;
// This is the statement I want to move along from
// if the user presses the return key without entering any input.
switch(mainMenuSelector){
case 1:
doSomething();
break;
case 1:
doSomething();
break;
case 2:
doSomething();
break;
case 3:
doSomething();
break;
}
}
return 0;
}
答案 0 :(得分：3)
std::string input;
while (std::getline(std::cin, input) && !input.empty()) { /* do stuff here */ }
你可能想要进一步验证输入是否有效，不只是有一堆空格等......
答案 1 :(得分：1)
在没有输入的情况下按Enter键会产生空字符串值。 你可以这样做（尝试并使其适应你的代码）：
#include <string>
#include <iostream>
using namespace std;
int main() {
string s;
getline(cin, s);
while(s != "") { // if the person hits enter, s == "" and leave the loop
cout << s << endl;
getline(cin, s);
}
return 0;
}
答案 2 :(得分：1)
如果你专门寻找使用流操作符的选项（而不是自己解析输入），你可以考虑使用std :: stringstream。例如：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- The above 3 meta tags *must* come first in the head; any other head content must come *after* these tags -->
<meta name="description" content="">
<meta name="author" content="">
<link rel="icon" href="../../favicon.ico">
<link rel="stylesheet" type="text/css" href="http://fonts.googleapis.com/css?family=Lobster|Oswald|Titillium Web|Roboto ">
<title>Starter Template for Bootstrap</title>
<!-- Bootstrap core CSS -->
<link href="../../dist/css/bootstrap.min.css" rel="stylesheet">
<!-- Custom styles for this template -->
<link href="starter-template.css" rel="stylesheet">
<!-- Just for debugging purposes. Don't actually copy these 2 lines! -->
<!--[if lt IE 9]><script src="../../assets/js/ie8-responsive-file-warning.js"></script><![endif]-->
<script src="../../assets/js/ie-emulation-modes-warning.js"></script>
<!-- HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries -->
<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js"></script>
<script src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
<![endif]-->
<script src="https://maps.googleapis.com/maps/api/js"></script>
<script>
function initialize() {
var mapCanvas = document.getElementById('map');
var myLatLng = {lat: 64.8370761, lng: -147.697845};
var mapOptions = {
center: myLatLng,
zoom: 16,
mapTypeId: google.maps.MapTypeId.ROADMAP
}
var map = new google.maps.Map(mapCanvas, mapOptions)
var marker = new google.maps.Marker({
position: myLatLng,
map: map,
title: "Nelson's Photography"
});
}
$('a[data-toggle="tab"]').on('shown.bs.tab', function(e) {
initialize();
});
</script>
</head>
<body>
<nav class="navbardos navbar-inverse navbar-fixed-top">
<div class="container">
<div class="navbar-header">
<a class="navbar-brand" href="#"><img src="/images/titlegraphic.jpg" class="logo"></a>
</div>
<ul class="nav navbar-navdos">
<li><a class="number">(907)452-3116</a></li>
<li><a>606 Bentley Drive | Fairbanks, AK</a></li>
</ul>
</div>
</nav>
<nav class="navbar navbar-inverse navbar-fixed-top">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
</div>
<div id="navbar" class="collapse navbar-collapse">
<ul class="nav nav-pills">
<li class="active"><a data-toggle="pill" href="#home">Home</a></li>
<li><a data-toggle="pill" href="#about">About</a></li>
<li><a data-toggle="pill" href="#services">Services</a></li>
<li><a data-toggle="pill" href="#portfolio">Portfolio</a></li>
<li><a data-toggle="pill" href="#contact">Contact</a></li>
</ul>
</div><!--/.nav-collapse -->
</div>
</nav>
<div class="tab-content">
<div id="home" class="tab-pane fade in active">
<div id="myCarousel" class="carousel slide" data-ride="carousel">
<!-- Indicators -->
<ol class="carousel-indicators">
<li data-target="#myCarousel" data-slide-to="0" class="active"></li>
<li data-target="#myCarousel" data-slide-to="1"></li>
<li data-target="#myCarousel" data-slide-to="2"></li>
</ol>
<div class="carousel-inner" role="listbox">
<div class="item active">
<img class="first-slide" src="/images/10x10reflect-lg.jpg" alt="First slide">
<div class="container">
<div class="carousel-caption">
<h1>Music Production Studio</h1>
<p></p>
<p><a class="btn btn-lg btn-primary" href="#" role="button">Learn More</a></p>
</div>
</div>
</div>
<div class="item">
<img class="second-slide" src="/images/11830247_10207115344978900_1142161344_n.jpg" alt="Second slide">
<div class="container">
<div class="carousel-caption">
<h1>Beat Gallery</h1>
<p></p>
<p><a class="btn btn-lg btn-primary" href="#" role="button">Listen</a></p>
</div>
</div>
</div>
<div class="item">
<img class="third-slide" src="/images/TMPstudio.jpg" alt="Third slide" style="width: 600px;">
<div class="container">
<div class="carousel-caption">
<h1>Studio Services</h1>
<p></p>
<p><a class="btn btn-lg btn-primary" href="#" role="button">Check-It Out</a></p>
</div>
</div>
</div>
</div>
<a class="left carousel-control" href="#myCarousel" role="button" data-slide="prev">
<span class="glyphicon glyphicon-chevron-left" aria-hidden="true"></span>
<span class="sr-only">Previous</span>
</a>
<a class="right carousel-control" href="#myCarousel" role="button" data-slide="next">
<span class="glyphicon glyphicon-chevron-right" aria-hidden="true"></span>
<span class="sr-only">Next</span>
</a>
</div><!-- /.carousel -->
</div>
<div id="about" class="tab-pane fade">
<img src="images/entry.jpg" id="AboutPic1">
<h1></h1>
<p id="lead">
Use this document as a way to quickly start any new project.<br>
All you get is this text and a mostly barebones HTML document.
</p>
</div>
<div id="services" class="tab-pane fade">
<h1>Services</h1>
<p class="lead">Use this document as a way to quickly start any new project.<br> All you get is this text and a mostly barebones HTML document.</p>
</div>
<div id="portfolio" class="tab-pane fade">
<h1>Portfolio</h1>
<p class="lead">Use this document as a way to quickly start any new project.<br> All you get is this text and a mostly barebones HTML document.</p>
</div>
<div id="contact" class="tab-pane fade">
<div id="map"></div>
<div id="contact-content">
<h1>We're looking forward to<br>
hearing from you!</h1><br>
<h2 style="text-decoration: underline">Phone Number:</h2>
<h2>edited</h2><br>
<h2 style="text-decoration: underline">Email:</h2>
<h2>edited</h2><br>
<h2 style="text-decoration: underline">Address:</h2>
<h2>
edited
</h2>
</div>
</div>
</div><!-- /.container -->
<!-- Bootstrap core JavaScript
================================================== -->
<!-- Placed at the end of the document so the pages load faster -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="../../dist/js/bootstrap.min.js"></script>
<!-- IE10 viewport hack for Surface/desktop Windows 8 bug -->
<script src="../../assets/js/ie10-viewport-bug-workaround.js"></script>
</body>
</html>