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std::function<R(Args...)>::operator bool

From cppreference.com
< cpp‎ | utility‎ | functional‎ | function
 
 
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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

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!

[edit] See also

checks if the std::move_only_function has a target
(public member function of std::move_only_function) [edit]
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