std::function<R(Args...)>::operator bool
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std::function
explicit operator bool() const noexcept;
(since C++11)
Checks whether *this stores a callable function target, i.e. is not empty.
Contents
[edit] Parameters
(none)
[edit] Return value
true if *this stores a callable function target, false otherwise.
[edit] Example
Run this code
#include <functional> #include <iostream> void sampleFunction() { std::cout << "This is the sample function!\n"; } void checkFunc(std::function <void()> const& func) { // Use operator bool to determine if callable target is available. if (func) { std::cout << "Function is not empty! Calling function.\n"; func(); } else std::cout << "Function is empty. Nothing to do.\n"; } int main() { std::function <void()> f1; std::function <void()> f2(sampleFunction); std::cout << "f1: "; checkFunc(f1); std::cout << "f2: "; checkFunc(f2); }
Output:
f1: Function is empty. Nothing to do. f2: Function is not empty! Calling function. This is the sample function!
[edit] See also
checks if the
(public member function of
std::move_only_function has a target (public member function of
std::move_only_function) [edit]