c++11 标准模板（STL）（std::basic_ostringstream）（四）

定义于头文件 <sstream>

template<     class CharT,     class Traits = std::char_traits<CharT> > class basic_ostringstream;		(C++11 前)
template<     class CharT,     class Traits = std::char_traits<CharT>,     class Allocator = std::allocator<CharT> > class basic_ostringstream;		(C++11 起)

类模板 std::basic_ostringstream 实现基于字符串的流上的输入与输出操作。它等效地存储一个 std::basic_string 的实例，并在其上进行输出操作。

在低层，该类实际上包装 std::basic_stringbuf 的未处理字符串设备到 std::basic_ostream 的高层接口中。提供到独有 std::basic_stringbuf 成员的完整接口。

亦定义对常用字符类型的二个特化： 

类型	定义
ostringstream	basic_ostringstream<char>
wostringstream	basic_ostringstream<wchar_t>

成员函数

交换两个字符串流

std::basic_ostringstream::swap

void swap( basic_ostringstream& other );

(C++11 起)

交换流与 other 的状态。

通过调用 basic_ostream<CharT, Traits>::swap(other) 和 rdbuf()->swap(*other.rdbuf()) 进行。

参数

other

-

要交换状态的流

返回值

（无）

调用示例

#include <sstream>
#include <string>
#include <iostream>

int main()
{
    //3) 以 str 的副本为底层字符串设备的初始内容。
    std::string string1 = "I am a handsome programmer";
    std::basic_ostringstream<char>
    basic_ostringstream1(string1, std::ios_base::out);
    std::cout << "basic_ostringstream1: "
              << basic_ostringstream1.str() << std::endl;
    std::cout << "basic_ostringstream1 rdstate: ";
    std::cout << basic_ostringstream1.rdstate() << std::endl;

    std::string string2 = "I am a super handsome guy";
    std::basic_ostringstream<char>
    basic_ostringstream2(string2, std::ios_base::out);
    std::cout << "basic_ostringstream2: "
              << basic_ostringstream2.str() << std::endl;
    std::cout << "basic_ostringstream2 rdstate: ";
    std::cout << basic_ostringstream2.rdstate() << std::endl;
    std::cout << std::endl;

    //交换流与 other 的状态。
    //通过调用 basic_istream<CharT, Traits>::swap(other)
    //和 rdbuf()->swap(*other.rdbuf()) 进行。
    basic_ostringstream1.swap(basic_ostringstream2);
    std::cout << "after swap: " << std::endl;

    std::cout << "basic_ostringstream1: "
              << basic_ostringstream1.str() << std::endl;
    std::cout << "basic_ostringstream1 rdstate: ";
    std::cout << basic_ostringstream1.rdstate() << std::endl;

    std::cout << "basic_ostringstream2: "
              << basic_ostringstream2.str() << std::endl;
    std::cout << "basic_ostringstream2 rdstate: ";
    std::cout << basic_ostringstream2.rdstate() << std::endl;

    return 0;
}

非成员函数

特化 std::swap 算法

std::swap(std::basic_ostringstream)

template< class CharT, class Traits, class Alloc > void swap( std::basic_ostringstream<CharT,Traits,Alloc>& lhs,            std::basic_ostringstream<CharT,Traits,Alloc>& rhs );

为 std::basic_ostringstream 特化 std::swap 算法。交换 lhs 与 rhs 的状态。等效地调用 lhs.swap(rhs) 。

参数

lhs, rhs

-

要交换状态的流

返回值

（无）

异常

（无）

调用示例 

#include <sstream>
#include <string>
#include <iostream>

int main()
{
    //3) 以 str 的副本为底层字符串设备的初始内容。
    std::string string1 = "I am a handsome programmer";
    std::basic_ostringstream<char>
    basic_ostringstream1(string1, std::ios_base::out);
    std::cout << "basic_ostringstream1: "
              << basic_ostringstream1.str() << std::endl;
    std::cout << "basic_ostringstream1 rdstate: ";
    std::cout << basic_ostringstream1.rdstate() << std::endl;

    std::string string2 = "I am a super handsome guy";
    std::basic_ostringstream<char>
    basic_ostringstream2(string2, std::ios_base::out);
    std::cout << "basic_ostringstream2: "
              << basic_ostringstream2.str() << std::endl;
    std::cout << "basic_ostringstream2 rdstate: ";
    std::cout << basic_ostringstream2.rdstate() << std::endl;
    std::cout << std::endl;

    //为 std::basic_ostringstream 特化 std::swap 算法。
    //交换 lhs 与 rhs 的状态。等效地调用 lhs.swap(rhs)
    std::swap(basic_ostringstream1, basic_ostringstream2);
    std::cout << "after swap: " << std::endl;

    std::cout << "basic_ostringstream1: "
              << basic_ostringstream1.str() << std::endl;
    std::cout << "basic_ostringstream1 rdstate: ";
    std::cout << basic_ostringstream1.rdstate() << std::endl;

    std::cout << "basic_ostringstream2: "
              << basic_ostringstream2.str() << std::endl;
    std::cout << "basic_ostringstream2 rdstate: ";
    std::cout << basic_ostringstream2.rdstate() << std::endl;

    return 0;
}

输出