< cpp‎ | container‎ | vector
void push_back( const T& value );
(1) (constexpr since C++20)
void push_back( T&& value );
(2) (since C++11)
(constexpr since C++20)

Appends the given element value to the end of the container.

1) The new element is initialized as a copy of value.
2) value is moved into the new element.

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

value - the value of the element to append
Type requirements
T must meet the requirements of CopyInsertable in order to use overload (1).
T must meet the requirements of MoveInsertable in order to use overload (2).

[edit] Return value


[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 T's move constructor 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.

(since C++11)


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;
    std::string s{"def"};
    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: ""

[edit] See also

constructs an element in-place at the end
(public member function) [edit]
removes the last element
(public member function) [edit]
creates a std::back_insert_iterator of type inferred from the argument
(function template) [edit]