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std::move_only_function:: operator bool

From cppreference.net
C++
Utilities library
Function objects
Function invocation
(C++17) (C++23)
Identity function object
(C++20)
Old binders and adaptors
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( until C++17* )
( until C++17* ) ( until C++17* ) ( until C++17* ) ( until C++17* )
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std::move_only_function
explicit operator bool ( ) const noexcept ;
(depuis C++23)

Vérifie si * this contient une cible appelable, c'est-à-dire n'est pas vide.

Table des matières

Paramètres

(aucun)

Valeur de retour

true si * this stocke une cible appelable, false sinon.

Exemple

Exécuter ce code 
#include <functional>
#include <iostream>
void sampleFunction()
{
    std::cout << "This is the sample function!\n";
}
void checkFunc(std::move_only_function<void() const> 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::move_only_function<void() const> f1{};
    std::move_only_function<void() const> f2{sampleFunction};
    std::cout << "f1: ";
    checkFunc(f1);
    std::cout << "f2: ";
    checkFunc(f2);
}

Sortie : 

f1: Function is empty. Nothing to do.
f2: Function is not empty! Calling function.
This is the sample function!

Voir aussi

(C++23)
compare un std::move_only_function avec nullptr
(fonction)
vérifie si une cible est contenue
(fonction membre publique de std::function<R(Args...)> )