如何通过引用传递从stringstream检索的字符串？

Question

I have following function

void myfun(std::string &str);

and I'm calling this functionas follows:

stringstream temp("");
temp << "some string data" ;
myfun(temp.str());

but I'm getting following error:

 error: no matching function for call to ‘myfun(std::basic_stringstream<char>::__string_type)’

and

no known conversion for argument 1 from ‘std::basic_stringstream<char>::__string_type {aka std::basic_string<char>}’ to ‘std::string& {aka std::basic_string<char>&}’

How can I pass this string by reference?

Answer 1

Why you need this? Why myfun receives reference, but not const ? std::stringstream::str returns std::string , that is temporary object and cannot be binded to lvalue-reference . You can send copy to function

std::string tmp = temp.str();
fun(tmp);

If you don't want to modify str in function fun you can rewrite it's signature to

void myfun(const std::string& str)

Answer 2

str returns by value, ie a copy of the internal string in temp . You can't pass a copy by non- const reference.

You can modify the function signature to:

void myfun(const std::string &str);