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!
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