public member function

std::vector::emplace_back

<vector>
template <class... Args>
void emplace_back (Args&&... args);
Construct and insert element at the end
Inserts a new element at the end of the vector, right after its current last element. This new element is constructed in place using args as the arguments for its constructor.

This effectively increases the container size by one, which causes an automatic reallocation of the allocated storage space if -and only if- the new vector size surpasses the current vector capacity.

A similar member function exists, push_back, which either copies or moves an existing object into the container.

Parameters

args
Arguments passed to the constructor of the new element.

Return value

none.

If a reallocation happens, the storage is allocated using the container's allocator, which may throw exceptions on failure (for the default allocator, bad_alloc is thrown if the allocation request does not succeed).

Example

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// vector::emplace_from
#include <iostream>
#include <vector>

int main ()
{
  std::vector<int> myvector = {10,20,30};

  myvector.emplace_back (100);
  myvector.emplace_back (200);

  std::cout << "myvector contains:";
  for (auto& x: myvector)
    std::cout << ' ' << x;
  std::cout << '\n';

  return 0;
}

Output:
myvector contains: 10 20 30 100 200

Complexity

Constant (amortized time, reallocation may happen).

If a reallocation happens, the reallocation is itself up to linear in the entire size.

Iterator validity

If a reallocation happens, all iterators, pointers and references related to this container are invalidated.
Otherwise, only the end iterator is invalidated, and all other iterators, pointers and references to elements are guaranteed to keep referring to the same elements they were referring to before the call.

Data races

The container is modified.
If a reallocation happens, all contained elements are modified.
Otherwise, no existing element is accessed, and concurrently accessing or modifying them is safe.

See also

vector::emplace_frontvector::insert_back