std::function<R(Args...)>::operator=
function& operator=( const function& other ); |
(1) | (since C++11) |
function& operator=( function&& other ); |
(2) | (since C++11) |
function& operator=( std::nullptr_t ) noexcept; |
(3) | (since C++11) |
template< class F > function& operator=( F&& f ); |
(4) | (since C++11) |
template< class F > function& operator=( std::reference_wrapper<F> f ) noexcept; |
(5) | (since C++11) |
Assigns a new target to std::function.
1) Assigns a copy of
target of
other, as if by executing
function(other).swap(*this);
2) Moves the
target of
other to
*this.
other is in a valid state with an unspecified value.
3) Drops the current
target.
*this is
empty after the call.
4) Sets the
target of
*this to the callable
f, as if by executing
function(std::forward<F>(f)).swap(*this);. This operator does not participate in overload resolution unless
f is
Callable for argument types
Args... and return type
R.
5) Sets the
target of
*this to a copy of
f, as if by executing
function(f).swap(*this);
Parameters
| other | - | another std::function object to copy the target of |
| f | - | a callable to initialize the target with |
| Type requirements | ||
-F must meet the requirements of Callable. |
||
Return value
*this.
Notes
Even before allocator support was removed from std::function in C++17, these assignment operators use the default allocator rather than the allocator of *this or the allocator of other (see LWG issue 2386).
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2132 | C++11 | the overload taking a Callable object might be ambiguous | constrained |
| LWG 2401 | C++11 | assignment operator from std::nullptr_t not required to be noexcept |
required |
See also
|
(C++23)
|
replaces or destroys the target (public member function of std::move_only_function<R(Args...) cv ref noexcept(noex)>) |
|
(removed in C++17)
|
assigns a new target (public member function) |
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