如何清空ostringstream中的内容

[boris963]

一个ostringstream流对象先读入了一些字符，再次用时想清空原有的字符，该用什么函数呢？

[Hot_Forever]

同意，os.str("")

[Hot_Forever]

用str函数:
ostringstream os;
os<<i<<j<<endl;
os.str();

[liu_feng_fly]

istream::ignore
istream& ignore( int nCount = 1, int delim = EOF );

Parameters

nCount

The maximum number of characters to extract.

delim

The delimiter character (defaults to EOF).

Remarks

Extracts and discards up to nCount characters. Extraction stops if the delimiter delim is extracted or the end of file is reached. If delim = EOF (the default), then only the end of file condition causes termination. The delimiter character is extracted.

basic_istream::ignore
basic_istream& ignore(streamsize n = 1,
int_type delim = T::eof());
The unformatted input function extracts up to n elements and discards them. If n equals numeric_limits<int>::max(), however, it is taken as arbitrarily large. Extraction stops early on end-of-file or on an element x such that T::to_int_type(x) compares equal to delim (which is also extracted). The function returns *this.

试以下这个

[boris963]

Hot_Forever(用钱砸死我吧)的方法是用来取得ostringstream中string的,但是不能把它清空.
liu_feng_fly(笑看风云 搏击苍穹 衔日月)说的ignore是istream中的,ostringstream继承自ostream,所以没有这个函数

[fangrk]

::str("");

[fangrk]

template<class charT, class traits = char_traits<charT>,
class Allocator = allocator<charT> >
class basic_ostringstream
: public basic_ostream<charT, traits> {
public:
typedef traits traits_type;
typedef charT char_type;
typedef typename traits::int_type int_type;
typedef typename traits::pos_type pos_type;
typedef typename traits::off_type off_type;
typedef basic_stringbuf<charT, traits, Allocator> sb_type;

typedef basic_ios<charT, traits> ios_type;
typedef basic_string<charT, traits, Allocator>
string_type;
explicit basic_ostringstream(ios_base::openmode which =
ios_base::out);
explicit basic_ostringstream(const string_type& str,
ios_base::openmode which =
ios_base::out);
virtual ~basic_ostringstream();
basic_stringbuf<charT,traits,Allocator> *rdbuf() const;

string_type str() const;
void str(const string_type& str);//就是这个啦！
};

[nirvana_li]

回复人： boris963(天行健) ( ) 信誉：100 2003-10-15 10:46:06 得分:0



Hot_Forever(用钱砸死我吧)的方法是用来取得ostringstream中string的,但是不能把它清空.
liu_feng_fly(笑看风云 搏击苍穹 衔日月)说的ignore是istream中的,ostringstream继承自ostream,所以没有这个函数

楼主说的都没错，我试了试，的确。
关注。虚心学习。

[Hot_Forever]

#include <iostream>
#include <sstream>
using namespace std;

int main()
{
ostringstream os;
os<<"dec:"<<15<<hex<<"hex:"<<15<<endl;
cout<<os.str();
os.str("");
cout<<os.str()<<endl;
return 0;
}
os.str("")已经清空了ostringstream

[Wolf0403]

干吗要清空它哩？超出 scope 直接释放了。或者干脆这样：重新构造一次好了^_^

[boris963]

谢谢大家帮忙解决了问题!