std::basic_string<CharT,Traits,Allocator>::swap
void swap( basic_string& other ); |
(until C++17) | |
|
void swap( basic_string& other )
noexcept
(
/* see below */
)
;
|
(since C++17) (constexpr since C++20) |
|
Exchanges the contents of the string with those of other. All iterators and references may be invalidated.
|
If
std::allocator_traits
<Allocator>
::
|
(since C++11) |
Parameters
| other | - | string to exchange the contents with |
Complexity
Constant.
Exceptions
No exception is thrown. |
(until C++11) |
|
No exception is thrown, unless the behavior is undefined. If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee). |
(since C++11) |
|
noexcept specification:
noexcept
(
std::allocator_traits
<Allocator>
::
propagate_on_container_swap
::
value
||
std::allocator_traits <Allocator> :: is_always_equal :: value ) |
(since C++17) |
Example
#include <iostream> #include <string> int main() { std::string a = "AAA"; std::string b = "BBBB"; std::cout << "Before swap:\n" "a = " << a << "\n" "b = " << b << "\n\n"; a.swap(b); std::cout << "After swap:\n" "a = " << a << "\n" "b = " << b << '\n'; }
Output:
Before swap: a = AAA b = BBBB After swap: a = BBBB b = AAA
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 403 | C++98 | swap() might throw an exception
|
no exception is thrown |
| LWG 535 | C++98 | swapping strings did not preserve the character orders | orders are also preserved |
| LWG 2151 (P1148R0) |
C++11 | no exception was thrown in the case of unequal non-propagating allocators |
the behavior is undefined in this case |
See also
| swaps the values of two objects (function template) |
|
| swaps two ranges of elements (function template) |
|
| swaps the contents (public member function of std::basic_string_view<CharT,Traits>) |