blocks|key|3231879|text|myStream.rdbuf()->in_avail()可用于获取准备从stringstream读取的可用字符数，您可以使用该计数来检查stringstream是否为“空”。我假设您实际上并不是在尝试检查值null。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3231880|例如，如果您想要从stringstream中提取一个int，然后查看是否有任何剩余的字符(即.非数字)您可以检查是否为myStream.rdbuf()->in_avail()+==+0。|3231881|这和你正在尝试做的事情相似吗？我不确定是否有更好的方法，但我过去也这样做过，对我来说效果很好。|3231882|https://en.cppreference.com/w/cpp/io/basic_streambuf/in_avail|3231883|编辑：我看到你刚刚更新了你的问题，因为我发了帖子。|BOLD|3231884|entityMap|0|LINK|mutability|MUTABLE|url^0|0|S|10|C|1W|C|2V|4|0|9|C|Q|3|1N|X|0|0|0|1P|0|0|0|3|0^^$0|@$1|2|3|4|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|14|8|@$9|15|A|16|B|C]|$9|17|A|18|B|C]|$9|19|A|1A|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|1B|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|1C|8|@]|D|@$9|1D|A|1E|1|1F]]|E|$]]|$1|L|3|M|5|6|7|1G|8|@$9|1H|A|1I|B|N]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|K]]]]

<code>myStream.rdbuf()-&gt;in_avail()</code> can be used to get the count of available characters ready to be read in from a <code>stringstream</code>, you can use that to check if your <code>stringstream</code> is "empty." I'm assuming you're not actually trying to check for the value <code>null</code>.

For example if you want to extract an <code>int</code> from a <code>stringstream</code> and then see if there were any left over characters (ie. non-numeric) you could check if <code>myStream.rdbuf()-&gt;in_avail() == 0</code>.

Is that something similar to what you're trying to do? I'm not sure if there's better ways but I've done this in the past and it's worked fine for me.

<a href="https://en.cppreference.com/w/cpp/io/basic_streambuf/in_avail" rel="noreferrer">https://en.cppreference.com/w/cpp/io/basic_streambuf/in_avail</a>

EDIT: I see you just updated your question as I posted.

blocks|key|3231983|text|一种简单的检查方法是查看流的字符串内容是否为空：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3231984|#include<assert.h>
#include<sstream>

int+main(){
std::stringstream+report_string;
report_string+<<+"";+//+an+empty+strin+g

//emptiness+check+of+stringstream
assert(report_string.str().empty());
}|code-block|syntax|javascript|3231985|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

An easy check would be to see if the string content of the stream is empty or not:

<pre><code>#include&lt;assert.h&gt;
#include&lt;sstream&gt;

int main(){
std::stringstream report_string;
report_string &lt;&lt; ""; // an empty strin g

//emptiness check of stringstream
assert(report_string.str().empty());
}
</code></pre>

blocks|key|3232135|text|这种方法是有效的，并且应该也适用于输出字符串：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3232136|ostringstream+report_string;

if+(report_string.tellp()+==+0)+{
++++//+do+something
}|code-block|syntax|javascript|3232137|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This method is efficient and should work with output strings as well:

<pre><code>ostringstream report_string;

if (report_string.tellp() == 0) {
 // do something
}
</code></pre>

blocks|key|4846561|text|一种方法是使用check+the+size+of+the+internal+string并与零进行比较。注意，这与AusCBlock建议的myStream.rdbuf()->in_avail()不同；in_avail()可以返回与流的实际大小不同的值(例如，如果内部缓冲区由多个不连续的内存块表示)。特别是，原则上，in_avail()+可以在非空的buffers中返回0(+stringbuf规范可能对此作了进一步的限制；我没有检查到那么多细节)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|BOLD|entityRanges|data|4846562|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/4432793/size-of-stringstream^0|1X|S|4E|A|58|9|4P|D|7|11|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|D]]|E|@$9|X|A|Y|1|Z]]|F|$]]|$1|G|3|-4|5|6|7|10|8|@]|E|@]|F|$]]]|H|$I|$5|J|K|L|F|$M|N]]]]

One way would be to <a href="https://stackoverflow.com/questions/4432793/size-of-stringstream">check the size of the internal string</a> and compare against zero. Note that this is different from <code>myStream.rdbuf()-&gt;in_avail()</code> as AusCBlock suggests; in_avail() can return a value different from the actual size of the stream (if, for example, the internal buffer is represented with multiple non-contiguous memory blocks). In particular, <code>in_avail()</code> can, in principle, return zero in non-empty buffers (it's possible that the <code>stringbuf</code> specification restricts this further; I have no checked in that much detail).

blocks|key|3232032|text|改用eof()。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3232033|示例代码：|3232034|stringstream+report_string;
if+(+!(report_string.eof())+)+
++++cout+<<+"report_string+EMPTY!+\n";|code-block|syntax|javascript|3232035|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Use eof() instead.

Sample Code:

<pre><code>stringstream report_string;
if ( !(report_string.eof()) ) 
 cout &lt;&lt; "report_string EMPTY! \n";
</code></pre>

blocks|key|847931|text|这通常是合理的和可读性的使用...|type|unstyled|depth|inlineStyleRanges|entityRanges|data|847932|report_string.str().empty()|code-block|syntax|javascript|847933|...but可能涉及到动态分配和将整个字符串复制到临时的，只会被丢弃。|847934|如果性能很重要，另一个选择是...|847935|report_string.peek()+==+decltype(report_string)::traits_type::eof()|847936|847937|这会查找尚未从流中提取的字符，忽略已经成功提取的输入+parsed/extracted|unordered-list-item|offset|length|style|BOLD|847938|847939|-+that's+different+from+testing+`report_string.str().empty()`,+which+still+"sees"+already-extracted+input|847940|​|847941|847942|如果之前的解析使流处于尚未提取的fail状态，则无论是否有更多未提取的字符|CODE|847943|，都将返回eof()|847944|entityMap^0|0|0|0|0|0|0|E|C|0|0|0|0|0|G|4|0|5|5|0^^$0|@$1|2|3|4|5|6|7|17|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|19|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|1A|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|1D|8|@$Q|1E|R|1F|S|T]]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]|$1|V|3|W|5|D|7|1H|8|@]|9|@]|A|$E|F]]|$1|X|3|Y|5|6|7|1I|8|@]|9|@]|A|$]]|$1|Z|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]|$1|10|3|11|5|P|7|1K|8|@$Q|1L|R|1M|S|12]]|9|@]|A|$]]|$1|13|3|14|5|6|7|1N|8|@$Q|1O|R|1P|S|12]]|9|@]|A|$]]|$1|15|3|-4|5|6|7|1Q|8|@]|9|@]|A|$]]]|16|$]]

It's normally reasonable and readable to use... 

<pre><code>report_string.str().empty()
</code></pre>

...but that may involve dynamic allocation and copying the entire string to a temporary, only to be thrown away.

If performance is important, another option is...

<pre><code>report_string.peek() == decltype(report_string)::traits_type::eof()
</code></pre>

<ul>
<li>this looks for a character not yet extracted from the stream, ignoring input that's already been successfully parsed/extracted

<ul>
<li>that's different from testing <code>report_string.str().empty()</code>, which still "sees" already-extracted input</li>
</ul></li>
<li>if earlier parsing left the stream in a <code>fail</code> state you haven't <code>clear()</code>ed, this will return <code>eof()</code> regardless of whether there are more unextracted characters</li>
</ul>

blocks|key|4846780|text|我知道这个问题很古老，而且已经得到了回答，但根据情况，可能还有另一种值得考虑的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4846781|当您测试字符串流是否为空时，您可以正确地对字符串流中的单个字符串或每一行执行某些操作；因此，您很可能会在字符串流上使用>>运算符或std::getline+...如果流是空的，那么它们的值就是false，因此您可以这样写：|offset|length|style|CODE|4846782|stringstream+report_string;

foo(report_string)//+some+functions+which+may+or+may+not+write+to+report_string

string+single_report;//string+to+read+to

bool+empty=true;//First+assume+it+was+empty
while(getline(report_string,single_report))//Alternatively+use+report_string>>single_report+if+you+don't+want+entire+lines
{
++++empty=false;//...it+wasn't+empty
++++bar(single_report);//Do+whatever+you+want+to+do+with+each+individual+appended+line+
}

if+(empty)
{
++++//...+whatever+you+want+to+do+if+the+stream+was+empty+goes+here
}|code-block|syntax|javascript|4846783|应该注意的是，这种方法假设您计划在stringstream中循环；如果您没有这样做，则不能使用此方法。|4846784|entityMap^0|0|1N|2|1T|C|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@$D|S|E|T|F|G]|$D|U|E|V|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|W|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|P|$]]

I know that this question is very old and already answered, but depending on the situation there might also be yet another approach worth considering:

When you are testing if a stringstream is empty, you properly intend to do something with either the individual strings or each line in the stringstream; thus you will most likely be using either the <code>&gt;&gt;</code> operator or <code>std::getline</code> on the stringstream... and if the stream is empty these simply have the value false, thus you could write:

<pre><code>stringstream report_string;

foo(report_string)// some functions which may or may not write to report_string

string single_report;//string to read to

bool empty=true;//First assume it was empty
while(getline(report_string,single_report))//Alternatively use report_string&gt;&gt;single_report if you don't want entire lines
{
 empty=false;//...it wasn't empty
 bar(single_report);//Do whatever you want to do with each individual appended line 
}

if (empty)
{
 //... whatever you want to do if the stream was empty goes here
}
</code></pre>

It should be noted that this approach assumes that you were planning on cycling through the stringstream; if you were not, then this approach can't be used.

blocks|key|845176|text|另一种方法呢？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|845177|如果您将ostringstream设置为可选类型，则可以在使用它之前检查它是否已被分配。|845178|想象一个名为lazy<>的类，它在需要的时候懒惰地构造一个对象，然后我们可以这样做：|offset|length|style|CODE|845179|int+main()
{
++++using+namespace+std;

++++auto+oss1+=+lazy<std::ostringstream>();
++++auto+oss2+=+lazy<std::ostringstream>();

++++use(oss1)+<<+"Hello";

++++if+(oss1)+cout+<<+use(oss1).str()+<<+endl;
++++if+(oss2)+cout+<<+use(oss2).str()+<<+endl;

++++if_used(oss1,+[](auto&+ss)+{+cout+<<+ss.str()+<<+endl;+});
++++if_used(oss2,
++++++++++++[](auto&+ss)+{+cout+<<+ss.str()+<<+endl;+},
++++++++++++[](auto&+oss)+{+cout+<<+"oss2+is+not+used"+<<+endl;+});

++++use(oss2)+<<+"Goodbye";
++++if_used(oss2,+[](auto&+ss)+{+cout+<<+ss.str()+<<+endl;+});

++++return+0;
}|code-block|syntax|javascript|845180|生成以下输出：|845181|Hello
Hello
oss2+is+not+used
Goodbye|845182|优势：|845183|845184|在不使用时不会冗余构造stringstream。如果未使用的字符串流随后被使用(通过常量引用)，|unordered-list-item|845185|optional会提供异常(通过常量引用)|845186|845187|下面是使用可定制构造函数的完整示例：|845188|我在optional中使用过std::experimental，但您也可以很容易地使用boost::optional。|845189|#include+<iostream>
#include+<experimental/optional>
#include+<utility>
#include+<type_traits>
#include+<sstream>

using+std::experimental::optional;

namespace+detail+{
++++template<class+T,+class+Constructor>
++++struct+lazy+final
++++{
++++++++template<class+Con+,+std::enable_if_t<+not+std::is_same<std::decay_t<Con>,+lazy>::value+>+*+=+nullptr>
++++++++lazy(Con&&+con)
++++++++:+_constructor(std::forward<Con>(con))
++++++++{}

++++++++T&+get()+{
++++++++++++if+(not+bool(_opt))+{
++++++++++++++++_opt+=+_constructor();
++++++++++++}
++++++++++++return+*_opt;
++++++++}

++++++++const+T&+get()+const+{
++++++++++++return+*_opt;
++++++++}

++++++++bool+used()+const+{
++++++++++++return+bool(_opt);
++++++++}

++++++++operator+bool()+const+{
++++++++++++return+used();
++++++++}

++++private:
++++++++Constructor+_constructor;
++++++++optional<T>+_opt;
++++};

++++template<class+T>
++++struct+default_construct+{
++++++++T+operator()()+const+{+return+T();+}
++++};

++++struct+no_action+{
++++++++template<class+T>
++++++++void+operator()(T&)+const+{+}
++++};
}


template<class+T,+class+Constructor+=+detail::default_construct<T>+>
auto+lazy(Constructor&&+con+=+detail::default_construct<T>())
{
++++return+detail::lazy<T,+std::decay_t<Constructor>>(std::forward<Constructor>(con));
}

template<class+T,+class+Constructor>
auto&+use(detail::lazy<T,+Constructor>&+l)
{
++++return+l.get();
}

template<class+T,+class+Constructor>
auto&+use(const+detail::lazy<T,+Constructor>&+l)
{
++++return+l.get();
}

template<class+T,+class+Constructor,+class+F,+class+Else+=+detail::no_action>
void+if_used(detail::lazy<T,+Constructor>&+l,+F&&+f,+Else&&+e+=+detail::no_action())
{
++++if+(l.used())
++++++++f(l.get());
++++else
++++++++e(l);
}

template<class+T,+class+Constructor,+class+F,+class+Else+=+detail::no_action>
void+if_used(const+detail::lazy<T,+Constructor>&+l,+F&&+f,+Else&&+e)
{
++++if+(l.used())
++++++++f(l.get());
++++else
++++++++e(l);
}

int+main()
{
++++using+namespace+std;

++++auto+oss1+=+lazy<std::ostringstream>();
++++auto+oss2+=+lazy<std::ostringstream>();

++++use(oss1)+<<+"Hello";

++++if+(oss1)+cout+<<+use(oss1).str()+<<+endl;
++++if+(oss2)+cout+<<+use(oss2).str()+<<+endl;

++++if_used(oss1,+[](auto&+ss)+{+cout+<<+ss.str()+<<+endl;+});
++++if_used(oss2,
++++++++++++[](auto&+ss)+{+cout+<<+ss.str()+<<+endl;+},
++++++++++++[](auto&+oss)+{+cout+<<+"oss2+is+not+used"+<<+endl;+});

++++use(oss2)+<<+"Goodbye";
++++if_used(oss2,+[](auto&+ss)+{+cout+<<+ss.str()+<<+endl;+});

++++return+0;
}|845190|entityMap^0|0|0|6|6|0|0|0|0|0|0|B|C|0|0|0|0|2|8|E|H|17|F|0|0^^$0|@$1|2|3|4|5|6|7|19|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1A|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|1B|8|@$F|1C|G|1D|H|I]]|9|@]|A|$]]|$1|J|3|K|5|L|7|1E|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|1F|8|@]|9|@]|A|$]]|$1|Q|3|R|5|L|7|1G|8|@]|9|@]|A|$M|N]]|$1|S|3|T|5|6|7|1H|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|V|3|W|5|X|7|1J|8|@$F|1K|G|1L|H|I]]|9|@]|A|$]]|$1|Y|3|Z|5|X|7|1M|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1N|8|@]|9|@]|A|$]]|$1|11|3|12|5|6|7|1O|8|@]|9|@]|A|$]]|$1|13|3|14|5|6|7|1P|8|@$F|1Q|G|1R|H|I]|$F|1S|G|1T|H|I]|$F|1U|G|1V|H|I]]|9|@]|A|$]]|$1|15|3|16|5|L|7|1W|8|@]|9|@]|A|$M|N]]|$1|17|3|-4|5|6|7|1X|8|@]|9|@]|A|$]]]|18|$]]

How about another approach? 

If you make the ostringstream an optional type you can check that its been assigned to before using it.

Imagine a class called <code>lazy&lt;&gt;</code> which lazily constructs an object when needed, then we could do this:

<pre><code>int main()
{
 using namespace std;

 auto oss1 = lazy&lt;std::ostringstream&gt;();
 auto oss2 = lazy&lt;std::ostringstream&gt;();

 use(oss1) &lt;&lt; "Hello";

 if (oss1) cout &lt;&lt; use(oss1).str() &lt;&lt; endl;
 if (oss2) cout &lt;&lt; use(oss2).str() &lt;&lt; endl;

 if_used(oss1, [](auto&amp; ss) { cout &lt;&lt; ss.str() &lt;&lt; endl; });
 if_used(oss2,
 [](auto&amp; ss) { cout &lt;&lt; ss.str() &lt;&lt; endl; },
 [](auto&amp; oss) { cout &lt;&lt; "oss2 is not used" &lt;&lt; endl; });

 use(oss2) &lt;&lt; "Goodbye";
 if_used(oss2, [](auto&amp; ss) { cout &lt;&lt; ss.str() &lt;&lt; endl; });

 return 0;
}
</code></pre>

yielding this output:

<pre><code>Hello
Hello
oss2 is not used
Goodbye
</code></pre>

Advantages:

<ul>
<li>no redundant construction of the <code>stringstream</code> when not used.</li>
<li>optional provides an exception if the unused stringstream is subsequently used (via const reference)</li>
</ul>

Full example below with customisable constructor:

I've used <code>std::experimental</code> for the <code>optional</code>, but you could just as easily use <code>boost::optional</code>.

<pre><code>#include &lt;iostream&gt;
#include &lt;experimental/optional&gt;
#include &lt;utility&gt;
#include &lt;type_traits&gt;
#include &lt;sstream&gt;

using std::experimental::optional;

namespace detail {
 template&lt;class T, class Constructor&gt;
 struct lazy final
 {
 template&lt;class Con , std::enable_if_t&lt; not std::is_same&lt;std::decay_t&lt;Con&gt;, lazy&gt;::value &gt; * = nullptr&gt;
 lazy(Con&amp;&amp; con)
 : _constructor(std::forward&lt;Con&gt;(con))
 {}

 T&amp; get() {
 if (not bool(_opt)) {
 _opt = _constructor();
 }
 return *_opt;
 }

 const T&amp; get() const {
 return *_opt;
 }

 bool used() const {
 return bool(_opt);
 }

 operator bool() const {
 return used();
 }

 private:
 Constructor _constructor;
 optional&lt;T&gt; _opt;
 };

 template&lt;class T&gt;
 struct default_construct {
 T operator()() const { return T(); }
 };

 struct no_action {
 template&lt;class T&gt;
 void operator()(T&amp;) const { }
 };
}


template&lt;class T, class Constructor = detail::default_construct&lt;T&gt; &gt;
auto lazy(Constructor&amp;&amp; con = detail::default_construct&lt;T&gt;())
{
 return detail::lazy&lt;T, std::decay_t&lt;Constructor&gt;&gt;(std::forward&lt;Constructor&gt;(con));
}

template&lt;class T, class Constructor&gt;
auto&amp; use(detail::lazy&lt;T, Constructor&gt;&amp; l)
{
 return l.get();
}

template&lt;class T, class Constructor&gt;
auto&amp; use(const detail::lazy&lt;T, Constructor&gt;&amp; l)
{
 return l.get();
}

template&lt;class T, class Constructor, class F, class Else = detail::no_action&gt;
void if_used(detail::lazy&lt;T, Constructor&gt;&amp; l, F&amp;&amp; f, Else&amp;&amp; e = detail::no_action())
{
 if (l.used())
 f(l.get());
 else
 e(l);
}

template&lt;class T, class Constructor, class F, class Else = detail::no_action&gt;
void if_used(const detail::lazy&lt;T, Constructor&gt;&amp; l, F&amp;&amp; f, Else&amp;&amp; e)
{
 if (l.used())
 f(l.get());
 else
 e(l);
}

int main()
{
 using namespace std;

 auto oss1 = lazy&lt;std::ostringstream&gt;();
 auto oss2 = lazy&lt;std::ostringstream&gt;();

 use(oss1) &lt;&lt; "Hello";

 if (oss1) cout &lt;&lt; use(oss1).str() &lt;&lt; endl;
 if (oss2) cout &lt;&lt; use(oss2).str() &lt;&lt; endl;

 if_used(oss1, [](auto&amp; ss) { cout &lt;&lt; ss.str() &lt;&lt; endl; });
 if_used(oss2,
 [](auto&amp; ss) { cout &lt;&lt; ss.str() &lt;&lt; endl; },
 [](auto&amp; oss) { cout &lt;&lt; "oss2 is not used" &lt;&lt; endl; });

 use(oss2) &lt;&lt; "Goodbye";
 if_used(oss2, [](auto&amp; ss) { cout &lt;&lt; ss.str() &lt;&lt; endl; });

 return 0;
}
</code></pre>

Just a quick question here guys. I've been searching to no avail so far.

A bit more info here:

<pre><code>stringstream report_string;

report_string &lt;&lt; "some string here...";
</code></pre>

In my code itself are various conditions for assigning values to the report_string variable.

I'd like to check whether it was assigned a value or not.

How do I check if a StringStream variable is empty/null?

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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伙计们，我有个小问题。到目前为止，我一直在寻找，但一无所获。这里有更多的信息：stringstream report_string;report_string << "some string here...";在我的代码中，有各种为report_string变量赋值的条件。我想检查它是否被赋值。

问如何检查StringStream变量是否为空？
EN

回答 8

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问如何检查StringStream变量是否为空？EN

回答 8

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问如何检查StringStream变量是否为空？
EN