std::vector<T,Allocator>::push_back

From cppreference.com
< cpp‎ | container‎ | vector

 
 
Containers library
Sequence
(C++11)
Associative
Unordered associative
Adaptors
Views
(C++20)
 
 
(1)
void push_back( const T& value );
(until C++20)
constexpr void push_back( const T& value );
(since C++20)
(2)
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 past-the-end iterator) are invalidated. Otherwise only the past-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 throws, the guarantee is waived and the effects are unspecified.

(since C++11)

Notes

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)).

Example

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

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)