table of contents
std::function::operatorbool(3) | C++ Standard Libary | std::function::operatorbool(3) |
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)
2022.07.31 | http://cppreference.com |