std::string swap() method

since C++20

// Non const version only
constexpr void swap( basic_string& other ) noexcept(/* see below */);

since C++17

// Non const version only
void swap( basic_string& other ) noexcept(/* see below */);

until C++17

// Non-const version only
void swap( basic_string& other );

Exchanges the contents of the string with those of other.

Possible invalidation

All iterators and references may be invalidated.

since C++11

Undefined Behavior

The behavior is undefined

if Allocator does not propagate on swap and the allocators of *this and other are unequal.

Parameters

• other - the string to exchange the contents with

Return value

(none)

Complexity

Constant - O(1).

Exceptions

since C++17

noexcept specification:

noexcept(std::allocator_traits<Allocator>::propagate_on_container_swap::value
|| std::allocator_traits<Allocator>::is_always_equal::value)

Example

Main.cpp

#include <string>
#include <iostream>
 
int main() 
{
    std::string a = "AAA";
    std::string b = "BBB";
 
    std::cout << "before swap" << '\n';
    std::cout << "a: " << a << '\n';
    std::cout << "b: " << b << '\n';
 
    a.swap(b);
 
    std::cout << "after swap" << '\n';
    std::cout << "a: " << a << '\n';
    std::cout << "b: " << b << '\n';
}

Output

before swap
a: AAA
b: BBB
after swap
a: BBB
b: AAA