std::move_only_function::operator()
From cppreference.com
< cpp | utility | functional | move only function
| R operator()( Args... args ) /*cv*/ /*ref*/ noexcept(/*noex*/); |
(since C++23) | |
Invokes the stored callable target with the parameters args. The /*cv*/, /*ref*/, and /*noex*/ parts of operator() are identical to those of the template parameter of std::move_only_function.
Equivalent to return std::invoke_r<R>(/*cv-ref-cast*/(f), std::forward<Args>(args)...);, where f is a cv-unqualified lvalue that denotes the target object of *this, and /*cv-ref-cast*/(f) is equivalent to:
- f if cv ref is either empty or &, or
- std::as_const(f) if cv ref is either const or const &, or
- std::move(f) if cv ref is &&, or
- std::move(std::as_const(f)) if cv ref is const &&.
The behavior is undefined if *this is empty.
Contents |
[edit] Parameters
| args | - | parameters to pass to the stored callable target |
[edit] Return value
std::invoke_r<R>(/*cv-ref-cast*/(f), std::forward<Args>(args)...).
[edit] Exceptions
Propagates the exception thrown by the underlying function call.
[edit] Example
The following example shows how std::move_only_function can passed to other functions by value. Also, it shows how std::move_only_function can store lambdas.
Run this code
#include <iostream> #include <functional> void call(std::move_only_function<int() const> f) // can be passed by value { std::cout << f() << '\n'; } int normal_function() { return 42; } int main() { int n = 1; auto lambda = [&n](){ return n; }; std::move_only_function<int() const> f = lambda; call(std::move(f)); n = 2; call(lambda); f = normal_function; call(std::move(f)); }
Output:
1 2 42
[edit] See also
| invokes the target (public member function of std::function<R(Args...)>)
| |
| calls the stored function (public member function of std::reference_wrapper<T>)
| |
| (C++17)(C++23) |
invokes any Callable object with given arguments and possibility to specify return type(since C++23) (function template) |
