NAME

std::function::operatorbool - std::function::operatorbool

Synopsis

explicit operator bool() const noexcept; (since C++11)

Checks whether *this stores a callable function target, i.e. is not empty.

Parameters

(none)

Return value

true if *this stores a callable function target, false otherwise.

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!

See also

operator bool checks if the std::move_only_function has a target
(C++23) (public member function of std::move_only_function)