[syncstream.syncbuf.assign]

# 31 Input/output library [[input.output]](./#input.output)

## 31.11 Synchronized output streams [[syncstream]](syncstream#syncbuf.assign)

### 31.11.2 Class template basic_syncbuf [[syncstream.syncbuf]](syncstream.syncbuf#assign)

#### 31.11.2.3 Assignment and swap [syncstream.syncbuf.assign]

[ð](#lib:operator=,basic_syncbuf)

`basic_syncbuf& operator=(basic_syncbuf&& rhs);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12742)

*Effects*: Calls emit() then
move assigns from rhs[.](#1.sentence-1)

After the move assignment *this has the observable state it would have had if
it had been move constructed from rhs ([[syncstream.syncbuf.cons]](syncstream.syncbuf.cons "31.11.2.2 Construction and destruction"))[.](#1.sentence-2)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12750)

*Postconditions*: 

- [(2.1)](#2.1)

rhs.get_wrapped() == nullptr is true.

- [(2.2)](#2.2)

this->get_allocator() == rhs.get_allocator() is true whenallocator_traits<Allocator>::propagate_on_container_move_assignment::value is true; otherwise, the allocator is unchanged.

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12763)

*Returns*: *this[.](#3.sentence-1)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12767)

*Remarks*: This assignment operator disassociates rhs from its wrapped stream buffer,
ensuring destruction of rhs produces no output[.](#4.sentence-1)

[ð](#lib:swap,basic_syncbuf)

`void swap(basic_syncbuf& other);
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12780)

*Preconditions*: Eitherallocator_traits<Allocator>​::​propagate_on_container_swap​::​value is true orthis->get_allocator() == other.get_allocator() is true[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12789)

*Effects*: Exchanges the state of *this and other[.](#6.sentence-1)
