std::inplace_vector<T,N>::try_push_back

 

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std::inplace_vector

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Member functions
inplace_vector::inplace_vector inplace_vector::~inplace_vector      inplace_vector::operator= inplace_vector::assign inplace_vector::assign_range Size and capacity inplace_vector::empty inplace_vector::size inplace_vector::max_size inplace_vector::capacity inplace_vector::resize inplace_vector::reserve inplace_vector::shrink_to_fit Iterators inplace_vector::begininplace_vector::cbegin inplace_vector::endinplace_vector::cend inplace_vector::rbegininplace_vector::crbegin inplace_vector::rendinplace_vector::crend	Element access inplace_vector::at inplace_vector::operator[] inplace_vector::front inplace_vector::back inplace_vector::data Modifiers inplace_vector::clear inplace_vector::erase inplace_vector::swap inplace_vector::insert inplace_vector::insert_range inplace_vector::emplace inplace_vector::emplace_back inplace_vector::try_emplace_back inplace_vector::unchecked_emplace_back inplace_vector::push_back inplace_vector::try_push_back inplace_vector::unchecked_push_back inplace_vector::pop_back inplace_vector::append_range inplace_vector::try_append_range (removed in C++26)
Non-member functions
erase(std::inplace_vector)erase_if(std::inplace_vector) swap(std::inplace_vector)	operator==operator<=>

 

constexpr std::optional<reference> try_push_back( const T& value );	(1)	(since C++26)
constexpr std::optional<reference> try_push_back( T&& value );	(2)	(since C++26)

Conditionally appends the given element value to the end of the container.

If size() == capacity() is true, there are no effects. Otherwise, appends an object of type T:

1) The new element is initialized as a copy of value.

2) value is moved into the new element.

No iterators or references are invalidated, except end(), which is invalidated if the insertion occurs.

Parameters

value	-	the value of the element to append
Type requirements
- T must meet the requirements of EmplaceConstructible.

Return value

std::nullopt if size() == capacity(), std::optional<reference>(std::in_place, back()) otherwise.

Complexity

Constant.

Exceptions

Any exception thrown by initialization of inserted element.

If an exception is thrown for any reason, these functions have no effect (strong exception safety guarantee).

Notes

Feature-test macro	Value	Std	Feature
__cpp_lib_inplace_vector	202603L	(C++26)	Better return type (std::optional<reference> instead of pointer) for try_push_back and try_emplace_back()

Example

Run this code

#include <cassert>
#include <inplace_vector>
#include <optional>
#include <string>

int main()
{
    std::inplace_vector<std::string, 2> pets;
    std::string dog{"dog"};

    std::optional<std::string&> p1 = pets.try_push_back("cat"); // overload (1)
    assert(*p1 == "cat" and pets.size() == 1);

    std::optional<std::string&> p2 = pets.try_push_back(std::move(dog)); // overload (2)
    assert(*p2 == "dog" and pets.size() == 2);

    assert(pets[0] == "cat" and pets[1] == "dog");
    assert(pets.size() == pets.capacity());

    std::optional<std::string&> p3 = pets.try_push_back("bug");
    assert(p3 == std::nullopt and pets.size() == 2);
}

See also

push_back	adds an element to the end (public member function)
emplace_back	constructs an element in-place at the end (public member function)
append_range	adds a range of elements to the end (public member function)
try_emplace_back	tries to construct an element in-place at the end (public member function)
try_append_range	tries to add a range of elements to the end (public member function)
unchecked_emplace_back	unconditionally constructs an element in-place at the end (public member function)
unchecked_push_back	unconditionally adds an element to 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)