NAME¶

std::vector::push_back - std::vector::push_back

Synopsis¶

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.

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).

Return value¶

(none)

Complexity¶

Amortized constant.

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 (since C++11)
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)).

Example¶

// Run this code

#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: ""

See also¶

emplace_back constructs an element in-place at the end
(C++11) (public member function)
pop_back removes the last element
(public member function)
back_inserter creates a std::back_insert_iterator of type inferred from the argument
(function template)