std::function<R(Args...)>::operator bool - cppreference.com (original) (raw)
| explicit operator bool() const noexcept; | | (since C++11) | | ---------------------------------------- | | ------------- |
Checks whether *this stores a callable function target, i.e. is not empty.
[edit] Parameters
(none)
[edit] Return value
true if *this stores a callable function target, false otherwise.
[edit] Example
#include
#include
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 std::move_only_function has a target (public member function of std::move_only_function) [edit] | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |