std::basic_ostream<CharT,Traits>::basic_ostream
|
(1) | |
|
(2) | (since C++11) |
|
(3) | (since C++11) |
1) Constructs the
basic_ostream object, assigning initial values to the base class by calling basic_ios::init(sb).
2) The copy constructor is protected, and is deleted. Output streams are not copyable.
3) The move constructor uses
basic_ios<CharT, Traits>::move(rhs) to move all basic_ios members, except for the rdbuf(), from rhs into *this. This move constructor is protected: it is called by the move constructors of movable output stream classes std::basic_ofstream and std::basic_ostringstream, which know how to correctly move the associated streambuffer.
Parameters
| sb | - | streambuffer to use as output sequence |
| rhs | - | basic_ostream to initialize from |
Notes
Because basic_ios::init(sb) sets badbit when sb is a null pointer, and because basic_ostream::sentry does nothing if the stream is already in a failed state, writing to a stream constructed from a null pointer sb is a no-op.
Example
#include <iostream>
#include <sstream>
#include <utility>
int main()
{
// ERROR: copy ctor is deleted
// std::ostream myout(std::cout);
// OK: shares buffer with cout
std::ostream myout(std::cout.rdbuf());
// ERROR: move constructor is protected
// std::ostream s2(std::move(std::ostringstream() << 7.1));
// OK: move ctor called through the derived class
std::ostringstream s2(std::ostringstream() << 7.1);
myout << s2.str() << '\n';
std::ostream dev_null{nullptr}; // see Notes above
dev_null << "no-op";
}Output:
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