std::function<R(Args...)>::operator bool
来自 cppreference.cn
< cpp | utility | functional | function
| explicit operator bool() const noexcept; |
(since C++11) | |
检查 *this 是否存储了可调用函数目标，即是否非空。
目录 |
[编辑] 参数
(无)
[编辑] 返回值
true 如果 *this 存储了可调用函数目标，否则为 false。
[编辑] 示例
运行此代码
#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); }
输出
f1: Function is empty. Nothing to do. f2: Function is not empty! Calling function. This is the sample function!
[编辑] 参见
检查 std::move_only_function 是否有目标( std::move_only_function 的公共成员函数) |
