std::vector push_back() method

since C++20

// (1) Non const version only
constexpr void push_back( T const& value );

// (2) Non const verison only
constexpr void push_back( T&& value );

since C++11

// (1) Non const version only
void push_back( T const& value );

// (2) Non const version only
void push_back( T&& value );

until C++11

// (1) Non const version only
void push_back( T const& value );

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.

Invalidation

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 is the container's element type in this list.

• (1) - T must meet the requirements of CopyInsertable.
• (2) - T must meet the requirements of MoveInsertable.

Return value

(none)

Complexity

Amortized constant - O(1).

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).

since C++11

If Ts 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.

Notes

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

Main.cpp

#include <vector>
#include <iostream>
#include <iomanip>
 
int main()
{
    std::vector<std::string> letters;
 
    letters.push_back("abc");
    std::string s = "def";
    letters.push_back(std::move(s));
 
    std::cout << "vector holds: ";
    for (auto&& i : letters) std::cout << std::quoted(i) << ' ';
    std::cout << "\nMoved-from string holds " << std::quoted(s) << '\n';
}

Output

vector holds: "abc" "def" 
Moved-from string holds ""