explicit operator bool() const noexcept; | (since C++11) |
Checks whether *this
stores a callable function target, i.e. is not empty.
(none).
true
if *this
stores a callable function target, false
otherwise.
#include <functional> #include <iostream> void sampleFunction() { std::cout << "This is the sample function!\n"; } void checkFunc( std::function<void()> &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!
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/utility/functional/function/operator_bool