std::function::operator bool
From cppreference.com
< cpp | utility | functional | function
| explicit operator bool() const;
|
(since C++11) | |
Checks whether *this stores a callable function target, i.e. is not empty.
Contents |
[edit] Parameters
(none)
[edit] Return value
true if *this stores a callable function target, false otherwise.
[edit] Exceptions
noexcept specification:
noexcept
[edit] Example
Run this code
#include <functional> #include <iostream> typedef std::function<void(int)> SomeVoidFunc; class C { public: C(SomeVoidFunc void_func = nullptr) : void_func_(std::move(void_func)) { if (!void_func_) { void_func_ = std::bind(&C::default_func, this, std::placeholders::_1); } void_func_(7); } void default_func(int i) { std::cout << i << '\n'; }; private: SomeVoidFunc void_func_; }; void user_func(int i) { std::cout << (i + 1) << '\n'; } int main() { C c1; C c2(user_func); }
Output:
7 8