c++ - How to implement StringBuilder class which to be able to accept IO manipulators

itemprop="text">

I wrote the following utility C++
class.

/*!
 * \brief The
            \b StringBuilder class is used for efficiently constructing long
 * strings
            out of many small ones. Internally it uses \b std::ostringstream and
 * its
            advantage compared to usage of raw \b std::ostringstream is that it is
 *
            capable to be used on single line and implicitly converted to \b std::string

            * everywhere this type is expected.

 * \code{.cpp}
 *
            void foo(const std::string& s);
 * foo(utils::StringBuilder("The answer
            is: ") << 42 << std::endl);
 * \endcode

            */
class StringBuilder
{
public:

            StringBuilder() = default;


 template             Args>
 explicit StringBuilder(Args&&... args)

            {
 append(std::forward(args)...);

            }

 template 
 StringBuilder&
            append(const T& arg)
 {
 _data <<
            arg;

 return *this;
 }

 template
            
 StringBuilder& append(const T& arg,
            Args&&... args)
 {
 _data << arg;

            append(std::forward(args)...);
 return *this;

            }


 std::string toString() const
 {

            return _data.str();
 }

 operator std::string()
            const
 {
 return toString();

            }


 template 

            StringBuilder& operator<<(const T& object)
 {
 return
            append(object);
 }

private:
 std::ostringstream
            _data;
};

cannot
compile. The error message is quite long to paste here, but it start
with:

main.cpp: In
function ‘int main()’: main.cpp:37:8: error: no match for
‘operator<<’
(operand types are ‘utils::StringBuilder’ and
‘’)
sb <<
endl;

and
ends with:

/usr/include/c++/4.8.3/bits/basic_string.h:2753:5: note: template

argument deduction/substitution failed: main.cpp:36:33: note: />‘utils::StringBuilder’ is not derived from
‘std::basic_ostream<_CharT,
_Traits>’
cout <<
(StringBuilder() <<
endl);

How
to make StringBuilder to be able to accept std::endl and other
IO manipulators?

itemprop="text">

class="normal">Answer

endl (as
well as the iomanip operands) is a
function.

Just write an overload like
this

StringBuilder&
            operator<<(ostream& func(ostream&))
{
 _data <<
            func;
 return
            *this;

}

..
or as an external operator like
this

StringBuilder&
            operator<<(StringBuilder& sb, ostream& func(ostream&))
            ...

...and it will
work for all of them