std::basic_ostream<CharT,Traits>::operator=

std::basic_ostream<CharT,Traits>::operator= - cppreference.com

From cppreference.com

`protected: basic_ostream& operator=( const basic_ostream& rhs ) = delete;`	(1)
`protected: basic_ostream& operator=( basic_ostream&& rhs );`	(2)	(since C++11)

1) The copy assignment operator is protected, and is deleted. Output streams are not CopyAssignable.

2) The move assignment operator exchanges all data members of the base class, except for

rdbuf()

, with rhs, as if by calling swap(*rhs). This move assignment operator is protected: it is only called by the move assignment operators of the derived movable output stream classes std::basic_ofstream and std::basic_ostringstream, which know how to correctly move-assign the associated streambuffers.

Parameters

rhs - the basic_ostream object from which to assign to *this

Example

#include <iostream>
#include <sstream>
#include <utility>

int main()
{
    std::ostringstream s;
//  std::cout = s;            // ERROR: copy assignment operator is deleted
//  std::cout = std::move(s); // ERROR: move assignment operator is protected
    s = std::move(std::ostringstream() << 42); // OK, moved through derived
    std::cout << s.str() << '\n';
}

Output:

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2067	C++11	1. the parameter type of overload (1) was `basic_ostream&` 2. the parameter type of overload (2) was `const basic_ostream&&`	1. added `const` 2. removed `const`