std::function<R(Args...)>::operator bool
来自cppreference.com
< cpp | utility | functional | function
| explicit operator bool() const noexcept; |
(C++11 起) | |
检查 *this 是否存储可调用函数对象，即非空。
参数
（无）
返回值
若 *this 存储可调用函数对象则为 true ，否则为 false 。
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()> &func ) { // 用 operator bool 确定可调用目标是否可用。 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!
