std::optional::emplace

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

 

Utilities library

Type support (basic types, RTTI, type traits)

Dynamic memory management

Error handling

Program utilities

Variadic functions

Date and time

Function objects

initializer_list (C++11)

bitset

hash (C++11)

Relational operators

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Pairs and tuples

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Swap, forward and move

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

std::optional

Member functions

optional::optional

optional::~optional

optional::operator=

Observers

optional::operator-> optional::operator*

optional::operator bool

optional::value

optional::value_or

Modifiers

optional::emplace

optional::swap

Non-member functions

operator== operator<

make_optional

swap

Helper classes

hash

 

template< class... Args > void emplace( Args&&... args );		(since C++14)
template< class U, class... Args > void emplace( std::initializer_list<U> ilist, Args&&... args );		(since C++14)

Constructs the contained value in-place. If *this is in engaged state before the call, the contained value is destroyed by calling its destructor.

1) Initializes the contained value by calling its constructor with args... as parameters.

2) Inilializes the contained value by calling its constructor with ilist and args... as parameters.

Parameters

args...	-	the arguments to pass to the constructor
ilist	-	the initializer list to pass to the constructor
Type requirements
- T must be constructible from Args...
- T must be constructible from std::initializer_list and Args...

Return value

(none)

Exceptions

Any exception thrown by the selected constructor of T. If an exception is thrown, *this is in disengaged state after the call.

See also

operator=	assigns contents (public member function)