R operator()( Args... args ) const; | (since C++11) |
Invokes the stored callable function target with the parameters args
.
Effectively does INVOKE<R>(f, std::forward<Args>(args)...)
, where f
is the target object of *this
and INVOKE
is the operation described in Callable.
args | - | parameters to pass to the stored callable function target |
None if R
is void
. Otherwise the return value of the invocation of the stored callable object.
std::bad_function_call
if *this
does not store a callable function target, i.e. !*this == true
. The following example shows how std::function
can passed to other functions by value. Also, it shows how std::function
can store lambdas.
#include <iostream> #include <functional> void call(std::function<int()> f) // can be passed by value { std::cout << f() << '\n'; } int normal_function() { return 42; } int main() { int n = 1; std::function<int()> f = [&n](){ return n; }; call(f); n = 2; call(f); f = normal_function; call(f); }
Output:
1 2 42
calls the stored function (public member function of std::reference_wrapper<T> ) |
|
(C++11) | the exception thrown when invoking an empty std::function (class) |
(C++17) | invokes any Callable object with given arguments (function template) |
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