std::vector<T,Allocator>::push_back
(constexpr since C++20)
Appends a copy of value to the end of the container.
If after the operation the new size() is greater than old capacity() a reallocation takes place, in which case all iterators (including the end() iterator) and all references to the elements are invalidated. Otherwise only the end() iterator is invalidated.
[edit] Parameters
[edit] Complexity
Amortized constant.
[edit] Exceptions
If an exception is thrown (which can be due to Allocator::allocate() or element copy/move constructor/assignment), this function has no effect (strong exception guarantee).
If the move constructor of T is not noexcept and T is not CopyInsertable into *this, vector will use the throwing move constructor. If it throws, the guarantee is waived and the effects are unspecified.
Notes
Some implementations throw std::length_error when push_back causes a reallocation that exceeds max_size (due to an implicit call to an equivalent of reserve (size () + 1)).
[edit] Example
#include <iomanip> #include <iostream> #include <string> #include <vector> int main() { std::vector <std::string > letters; letters.push_back("abc"); std::string s{"def"}; letters.push_back(std::move(s)); std::cout << "std::vector letters holds: "; for (auto&& e : letters) std::cout << std::quoted (e) << ' '; std::cout << "\nMoved-from string s holds: " << std::quoted (s) << '\n'; }
Possible output:
std::vector letters holds: "abc" "def" Moved-from string s holds: ""