std::basic_ostream<CharT,Traits>::basic_ostream
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< cpp | io | basic ostream
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explicit basic_ostream( std::basic_streambuf <CharT, Traits>* sb );
(1)
protected:
basic_ostream( const basic_ostream& rhs ) = delete;
(2)
(since C++11)
basic_ostream( const basic_ostream& rhs ) = delete;
protected:
basic_ostream( basic_ostream&& rhs );
(3)
(since C++11)
basic_ostream( basic_ostream&& rhs );
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.[edit] Parameters
sb
-
streambuffer to use as output sequence
rhs
-
basic_ostream to initialize from
[edit] 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.
[edit] Example
Run this code
#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:
7.1