vector& operator=( const vector& other ); | (1) | |
(2) | ||
vector& operator=( vector&& other ); | (since C++11) (until C++17) | |
vector& operator=( vector&& other ) noexcept(/* see below */); | (since C++17) | |
vector& operator=( std::initializer_list<T> ilist ); | (3) | (since C++11) |
Replaces the contents of the container.
other
.If std::allocator_traits<allocator_type>::propagate_on_container_copy_assignment::value
is true
, the target allocator is replaced by a copy of the source allocator. If the target and the source allocators do not compare equal, the target (*this
) allocator is used to deallocate the memory, then other
's allocator is used to allocate it before copying the elements. (since C++11).other
using move semantics (i.e. the data in other
is moved from other
into this container). other
is in a valid but unspecified state afterwards. If std::allocator_traits<allocator_type>::propagate_on_container_move_assignment::value
is true
, the target allocator is replaced by a copy of the source allocator. If it is false
and the source and the target allocators do not compare equal, the target cannot take ownership of the source memory and must move-assign each element individually, allocating additional memory using its own allocator as needed. In any case, all elements originally present in *this
are either destroyed or replaced by elementwise move-assignment.ilist
.other | - | another container to use as data source |
ilist | - | initializer list to use as data source |
*this
.
*this
and other
.*this
unless the allocators do not compare equal and do not propagate, in which case linear in the size of *this
and other
*this
and ilist
. Exceptions2)noexcept specification: noexcept(std::allocator_traits<Allocator>::propagate_on_container_move_assignment::value | (since C++17) |
After container move assignment (overload (2)), unless elementwise move assignment is forced by incompatible allocators, references, pointers, and iterators (other than the end iterator) to other
remain valid, but refer to elements that are now in *this
. The current standard makes this guarantee via the blanket statement in §23.2.1[container.requirements.general]/12, and a more direct guarantee is under consideration via LWG 2321.
The following code uses operator=
to assign one std::vector
to another:
#include <vector> #include <iostream> void display_sizes(const std::vector<int>& nums1, const std::vector<int>& nums2, const std::vector<int>& nums3) { std::cout << " nums1: " << nums1.size() << " nums2: " << nums2.size() << " nums3: " << nums3.size() << '\n'; } int main() { std::vector<int> nums1 {3, 1, 4, 6, 5, 9}; std::vector<int> nums2; std::vector<int> nums3; std::cout << "Initially:\n"; display_sizes(nums1, nums2, nums3); // copy assignment copies data from nums1 to nums2 nums2 = nums1; std::cout << "After assigment:\n"; display_sizes(nums1, nums2, nums3); // move assignment moves data from nums1 to nums3, // modifying both nums1 and nums3 nums3 = std::move(nums1); std::cout << "After move assigment:\n"; display_sizes(nums1, nums2, nums3); }
Output:
Initially: nums1: 6 nums2: 0 nums3: 0 After assigment: nums1: 6 nums2: 6 nums3: 0 After move assigment: nums1: 0 nums2: 6 nums3: 6
constructs the vector (public member function) |
|
assigns values to the container (public member function) |
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