void push_back( const T& value );
(until C++20)
constexpr void push_back( const T& value );
(since C++20)
void push_back( T&& value );
(since C++11)
(until C++20)
constexpr void push_back( T&& value );
(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 the new size() is greater than capacity() then all iterators and references (including the end() iterator) are invalidated. Otherwise only the end() iterator is invalidated.


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).

Return value



Amortized constant.


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)


Calling push_back will cause reallocation (when size()+1 > capacity()), so some implementations also throw std::length_error when push_back causes a reallocation that would exceed max_size (due to implicitly calling an equivalent of reserve(size()+1)).


#include <vector>
#include <iostream>
#include <iomanip>
#include <string>
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: ""

See also

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

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