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

 

C++

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Named requirements

Feature test macros (C++20)

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Technical specifications

Symbols index

External libraries

 

Containers library

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array (C++11)

vector

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forward_list (C++11)

list

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unordered_set (C++11)

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std::vector

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vector::vector

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Element access

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vector::data

Iterators

vector::beginvector::cbegin (C++11)

vector::endvector::cend (C++11)

vector::rbeginvector::crbegin (C++11)

vector::rendvector::crend (C++11)

Capacity

vector::empty

vector::size

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vector::capacity

vector::shrink_to_fit (C++11)

Modifiers

vector::clear

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vector::emplace (C++11)

vector::erase

vector::push_back

vector::emplace_back (C++11)

vector::pop_back

vector::resize

vector::swap

Non-member functions

std::swap

eraseerase_if (C++20)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

Deduction guides(C++17)

 

	(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

Run this code

#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

emplace_back (C++11)	constructs an element in-place at the end (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)