std::move_only_function:: operator bool

检查 * this 是否存储了可调用目标，即非空状态。

参数

(无)

返回值

若 * this 存储了可调用目标则为 true ，否则为 false 。

示例

#include <functional>
#include <iostream>
void sampleFunction()
{
    std::cout << "This is the sample function!\n";
}
void checkFunc(std::move_only_function<void() const> const& func)
{
    // 使用 operator bool 判断是否包含可调用目标
    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);
}

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

参见