小编Lon*_* Bu的帖子

#include <functional>
#include <iostream>
#include <type_traits>

using cb_t = std::function<void ()>;

template<typename CB_T, std::enable_if_t<std::is_constructible<cb_t, CB_T>::value, bool> = true>
void
on_my_write(int a, int b, CB_T&& cb) {
    std::cout << "on_my_write:" << a << ", " << b << std::endl;
}
 

template<typename CB_T,  std::enable_if_t<std::is_constructible<cb_t, CB_T>::value, bool> = true>
void foo(CB_T&& cb) {
    auto b = std::bind(&on_my_write<CB_T>, std::placeholders::_1, std::placeholders::_2, std::forward<CB_T>(cb));
    b(1, 2);
}

int main() {
  
    foo([]{});

    return 0;
}

用命令行编译这个

g++ ./try1.cpp -std=c++17

给我：

./try1.cpp: In instantiation of ‘void foo(CB_T&&) [with CB_T …

这有效:

$('h1').click(function(){console.log("clicked");};

这不是:

var h1 = $('h1');
h1[0].click(function(){console.log("clicked");}

这又有效:

var h1=$('h1');
var h2 = $(h1[0]).click(function() {console.log("clicked");}

有人会解释原因吗？

非常感谢!

干杯龙