blocks|key|1990868|text|iostreams库中的getline变体不支持字符串作为目标，因此字符串库定义了一个支持的变体。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1990869|entityMap^0|C|7|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

The <code>getline</code> variant inside the iostreams library does not support strings as targets, so the string library defined a variant that does.

blocks|key|1990877|text|全局getline()函数适用于C%2B%2B+std::string对象。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1990878|istream::getline()方法使用“经典”C字符串(指向char的指针)。|style|CODE|1990879|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cplusplus.com/reference/string/getline/|1|http://www.cplusplus.com/reference/string/string/|2|http://www.cplusplus.com/reference/iostream/istream/getline/^0|2|9|0|K|B|1|0|X|4|0|I|2|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]|$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@$A|11|B|12|F|G]]|9|@$A|13|B|14|1|15]]|C|$]]|$1|H|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]|P|$5|K|L|M|C|$N|Q]]|R|$5|K|L|M|C|$N|S]]]]

The global <a href="http://www.cplusplus.com/reference/string/getline/" rel="noreferrer">getline()</a> function works with C++ <a href="http://www.cplusplus.com/reference/string/string/" rel="noreferrer">std::string</a> objects.

The <a href="http://www.cplusplus.com/reference/iostream/istream/getline/" rel="noreferrer">istream::getline()</a> methods work with "classic" C strings (pointers to <code>char</code>).

blocks|key|1990904|text|是的，现代的C%2B%2B方法是使用自由函数并输入std::string。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1990905|但是IOStream有比std::string更长的历史(标准版本至少是相同设计的第三个版本)，而这段历史解释了为什么事情是这样的。|1990906|(+getline成员的优点是它不意味着动态分配；该特性有时可能很方便，但可能不足以在从头开始的设计中证明它的合理性)。|1990907|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

Yes the modern C++ way is to use the free function and input an std::string.

But IOStream has a far longer history (the standard version is at least the third incarnation of the same design) than std::string and that history explain why things are the way they are.

(The getline member has the advantage that it doesn't imply dynamic allocation; that characteristic can be handy at time but would probably not be enough to justify it in a from scratch design).

blocks|key|1990927|text|请记住，标准库由3个(主要)部分组成:+IOStream、字符串和STL，外加一些好东西和C-headers。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1990928|我看不出这些部分松散耦合有什么奇怪的(尽管我希望不是这样)。|1990929|其他不一致之处包括：std::string::length与std::string::size，后者是为了与STL接口兼容而添加的，而前者是为了与旧代码兼容而保留的。|offset|length|style|CODE|1990930|entityMap^0|0|0|A|J|U|H|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|N|8|@$F|O|G|P|H|I]|$F|Q|G|R|H|I]]|9|@]|A|$]]|$1|J|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|K|$]]

Bear in mind that the Standard library is composed from 3 (main) parts: IOStream, String and STL, plus some tossed in goodies and the C-headers.

I don't see anything weird in having those parts loosely coupled (though I wish it was not the case).

Other incongruities include: <code>std::string::length</code> vs <code>std::string::size</code>, the latter having been added for interface compatibility with the STL and the former having been retained for compatibility with older code.

blocks|key|1990940|text|这是一个常见的界面设计问题。cin.getline()是发出请求的一种自然方式，但是为了避免使流代码依赖于<string>，不能提供cin.getline(std::string&)函数。一旦字符串进入作用域，就可以添加独立的getline(cin,+s)。对于char*来说不是问题，因为#include没有任何东西--不管怎么说，都是语言的一部分。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1990941|在某些方面，当语言允许以后的代码向现有类添加更多功能(例如Ruby)时，这是件好事，但在其他方面，去本地化会带来负面影响，而且会影响可维护性。当然还有关于最小成员函数和大量独立函数的流行论点:我个人认为不应该让界面变得不那么直观和表达，而是每个函数都有自己的特点。|1990942|entityMap^0|E|D|1H|8|1U|P|35|F|3N|5|41|8|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|W|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|I|$]]

It's a common interface-design problem. <code>cin.getline()</code> is a natural way to make the request, but to avoid making the stream code dependent on <code>&lt;string&gt;</code>, no <code>cin.getline(std::string&amp;)</code> function can be offered. The free-standing <code>getline(cin, s)</code> can later be added once strings have been brought into scope. Not a problem for <code>char*</code> as there's nothing to <code>#include</code> - all part of the language anyway.

In some ways, it's nice when languages allow later code to add further functions to existing classes (e.g. Ruby), but in other ways the delocalisation bites and, well, compromises maintainability. Then of course there's the popular argument for minimal member functions and lots of free-standing functions: I personally think it shouldn't be taken so far as to make the interface less intuitive and expressive, but each to their own.

blocks|key|1990965|text|来源：https://www.reddit.com/r/learnprogramming/comments/4fx64h/is_there_a_difference_between_cingetline_and/|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1990966|成员函数cin.getline()使用C字符串(即字符数组)，而自由函数std::getline()使用C%2B%2B字符串(即std：：string)。在学习C%2B%2B时，根本不应该使用C字符串，这意味着不应该使用cin.getline()。|1990967|getline()从输入流中读取字符串，直到某个分隔符。默认情况下，分隔符是'\n‘，如果您只是要传递换行符，则没有理由指定第三个参数。除了检查分隔符之外，它并不知道或关心字符串中包含的内容。如果您想尝试将字符串解析为整数或浮点值，您当然可以在从流中读取后执行此操作，但这不是std：：getline()的工作，它只是读取字符串。|1990968|entityMap|0|LINK|mutability|MUTABLE|url|https://www.reddit.com/r/learnprogramming/comments/4fx64h/is_there_a_difference_between_cingetline_and/^0|3|2V|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|U|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]]]

Source:<a href="https://www.reddit.com/r/learnprogramming/comments/4fx64h/is_there_a_difference_between_cingetline_and/" rel="nofollow noreferrer">https://www.reddit.com/r/learnprogramming/comments/4fx64h/is_there_a_difference_between_cingetline_and/</a> 

The member function cin.getline() works with C strings (i.e. arrays of char) whereas the free function std::getline() works with C++ strings (i.e. std::string.) You should not be using C strings at all when learning C++, which means you should not be using cin.getline().

std::getline() reads a string from an input stream up to some delimiter. The delimiter by default is '\n' and there's no reason to specify that third argument if you're just going to pass the newline character. It doesn't know or care what is contained in that string, other than checking for the delimiter. If you want to attempt to parse that string as an integer or a floating point value you can certainly do that after reading from the stream, but that's not std::getline()'s job. It just reads a string.

Every time I do a quick snippet of C++ code line 

<pre><code>std::string s;
cin &gt;&gt; s;
</code></pre>

I curse myself because I forgot it stops at the whitespace rather than getting an entire line.

Then, on remembering <code>getline</code>, I invariably become confused as to the two varieties:

<pre><code>std::string s;
getline (std::cin, s);
</code></pre>

and:

<pre><code>char cs[256];
std::cin.getline (cs, sizeof (cs));
</code></pre>

Is there actually a difference between these two other than the data type?

It seems to me the C++ way should be the former. Under what circumstances would I use the latter, given that I probably should be using real strings instead
of null-terminated character arrays anyway?

And, since input should really be the purview of the input streams, why isn't the former part of <code>istream</code>?

Why are there two different getline() functions (if indeed there are)?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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每次我做一小段C++代码行std::string s;cin >> s;我咒骂自己，因为我忘记了它只停留在空格，而不是整行。然后，一想起getline，我总是对这两种变体感到困惑：std::string s;getline (std::cin, s);和：char cs[256];std::cin.getline (c...

问为什么会有两个不同的getline()函数(如果确实有)？
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问为什么会有两个不同的getline()函数(如果确实有)？EN