C++中std :: cin对象的规则是什么？

我正在编写一个小程序供个人使用,用于练习学习C++及其功能,一个MLA引文生成器(我正在写一篇有几十次引用的大型论文).

由于缺乏更好的方法(我不懂课程或在你的主要内部使用其他.cpp文件,所以不要打扰告诉我,当我有更多时间时我会继续工作),我正在写作每种引用的功能.如果我有更多的时间,我可能会将其分解为每个重用代码的函数.

我的问题是:std :: cin对象是如何工作的？我目前正在使用std :: cin >>读取我希望成为单个单词的字符串,以及带有空格的字符串的getline(std :: cin,string).但是,我没有得到正确的输出.我只是想知道std :: cin如何工作以及为什么我会意外地跳过一些输入(例如,它跳过webPage而不是给我一个机会输入它).

void webCit() {
    std::cout << "Leave any unknowns blank.\n";

    std::cout << "Author last name: ";
    std::string lastName;
    std::cin >> lastName;

    if (lastName.size() != 0) {
        lastName = lastName + ", ";
    }


    std::cout << "Author first name: ";
    std::string firstName;
    std::cin >> firstName;

    if (firstName.size() != 0) {
        firstName = firstName + ". ";
    }


    std::cout << "Article title: ";
    std::string articleTitle;
    getline(std::cin, articleTitle);

    if (articleTitle.size() != 0) {
        articleTitle = "\"" + articleTitle + ".\" ";
    }

    std::cout << "Title of web page: ";
    std::string pageTitle;
    std::cin >> pageTitle;

    if (pageTitle.size() != 0) {
        pageTitle = pageTitle + ". ";
    }

    std::cout << "Publication date: ";
    std::string publicationDate;
    getline(std::cin, publicationDate);

    if (publicationDate.size() != 0) {
        publicationDate = publicationDate + ". ";

    }

    std::cout << "Web address: ";
    std::string webAddress;
    getline(std::cin, webAddress);

    webAddress = "<" + webAddress + ">. ";

    std::cout << "Date accessed: ";
    std::string dateAccessed;
    getline(std::cin, dateAccessed);

    if (dateAccessed.size() != 0) {
        dateAccessed = dateAccessed + ". ";
    }

    std::string citation =
        lastName + firstName + articleTitle + pageTitle + publicationDate + webAddress + dateAccessed;

    std::cout << citation; //TEST; remove after
}

编辑:I/O.

Leave any unknowns blank.
Author last name: Hooked
Author first name: Jerbear
Article title: Title of web page: title
Publication date: Web address: www.win.com
Date accessed: 4/29/09
Hooked, Jerbear. Title. . 4/29/09. 

正如你所看到的,出现问题,因为我的输入被忽略了.

这里发生的事情是std::cin >> firstName;只读取但不包括第一个空白字符,'\n'当你按Enter键时包含换行符(或),所以当它到达时getline(std::cin, articleTitle);,'\n'仍然是下一个字符std::cin,并getline()立即返回.

// cin = "Bloggs\nJoe\nMan of Steel, Woman of Kleenex\n"
std::cin >> lastName;
std::cin >> firstName;
// firstName = "Joe", lastName = "Bloggs", cin = "\nMan of Steel, Woman of Kleenex\n"
getline(std::cin, articleTitle);
// articleTitle = "", cin = "Man of Steel, Woman of Kleenex\n"

在调用getline()之前添加' std::cin >> std::ws'(ws意思是white space)可以解决问题:

std::cin >> firstName >> std::ws;
getline(std::cin, articleTitle);

但是如果你在论证中这样做,你会更容易看到你错过了它:

std::cin >> firstName;
getline(std::cin >> std::ws, articleTitle);