最简单的方法是在开始时将参数打包成元组,然后将元组传递给test_signal_daisy_chain_impl
:
template < typename... Fargs,
typename T, typename... Sargs>
void test_signal_daisy_chain_impl(const std::tuple<Fargs...> & fargs,
T* t, void(T::*t_signal)(Fargs...),
Sargs &&... sargs)
{
std::apply([&](auto ...params)
{
(t->*t_signal)(params...);
}, fargs);
if constexpr (sizeof...(Sargs) > sizeof...(Fargs))
test_signal_daisy_chain_impl(fargs, std::forward<Sargs>(sargs)...);
}
template <std::size_t I, typename Ret, typename T, typename... Qargs>
Ret get_last_n(T && t, Qargs && ...qargs)
{
static_assert(I <= sizeof...(Qargs) + 1,
"Not enough parameters to pass to the signal function");
if constexpr(sizeof...(Qargs)+1 == I)
return {std::forward<T>(t), std::forward<Qargs>(qargs)...};
else
return get_last_n<I, Ret>(std::forward<Qargs>(qargs)...);
}
template <typename T, typename... Fargs,
typename... Qargs>
void test_signal_daisy_chain(T* t, void(T::*t_signal)(Fargs...),
Qargs&&... qargs)
{
static_assert((sizeof...(Qargs) - sizeof...(Fargs)) % 2 == 0,
"Expecting even number of parameters for object-signal pairs");
if constexpr ((sizeof...(Qargs) - sizeof...(Fargs)) % 2 == 0) {
auto fargs = get_last_n<sizeof...(Fargs), std::tuple<Fargs...>>(
std::forward<Qargs>(qargs)...);
test_signal_daisy_chain_impl(fargs, t, t_signal,
std::forward<Qargs>(qargs)...);
}
}
用法:
class Object {
public:
void print_vec(const std::vector<int> & vec)
{
for (auto elem: vec) std::cout << elem << ", ";
}
void signal1(const std::vector<int> & vec)
{
std::cout << "signal1(";
print_vec(vec);
std::cout << ")\n";
}
void signal2(const std::vector<int> & vec)
{
std::cout << "signal2(";
print_vec(vec);
std::cout << ")\n";
}
void signal_int1(int a, int b)
{ std::cout << "signal_int1(" << a << ", " << b << ")\n"; }
void signal_int2(int a, int b)
{ std::cout << "signal_int2(" << a << ", " << b << ")\n"; }
void signal_int3(int a, int b)
{ std::cout << "signal_int3(" << a << ", " << b << ")\n"; }
};
int main()
{
Object object;
test_signal_daisy_chain(&object, &Object::signal1,
&object, &Object::signal2 ,
std::vector{1,2,3});
test_signal_daisy_chain(&object, &Object::signal_int1,
&object, &Object::signal_int2 ,
&object, &Object::signal_int3,
1,2);
}
编辑1
由于C++11是一个硬约束条件,因此有一个更加丑陋的解决方案,基于相同的原则。必须实现诸如std :: apply
和std :: make_index_sequence
之类的内容。使用重载代替if constexpr(....)
:
template <std::size_t ...I>
struct indexes
{
using type = indexes;
};
template<std::size_t N, std::size_t ...I>
struct make_indexes
{
using type_aux = typename std::conditional<
(N == sizeof...(I)),
indexes<I...>,
make_indexes<N, I..., sizeof...(I)>>::type;
using type = typename type_aux::type;
};
template <typename Tuple, typename T, typename Method, std::size_t... I>
void apply_method_impl(
Method t_signal, T* t, const Tuple& tup, indexes<I...>)
{
return (t->*t_signal)(std::get<I>(tup)...);
}
template <typename Tuple, typename T, typename Method>
void apply_method(const Tuple & tup, T* t, Method t_signal)
{
apply_method_impl(
t_signal, t, tup,
typename make_indexes<
std::tuple_size<Tuple>::value>::type{});
}
template < typename... Fargs, typename... Sargs>
typename std::enable_if<(sizeof...(Fargs) == sizeof...(Sargs)), void>::type
test_signal_daisy_chain_impl(const std::tuple<Fargs...> & ,
Sargs &&...)
{}
template < typename... Fargs,
typename T, typename... Sargs>
void test_signal_daisy_chain_impl(const std::tuple<Fargs...> & fargs,
T* t, void(T::*t_signal)(Fargs...),
Sargs &&... sargs)
{
apply_method(fargs, t, t_signal);
test_signal_daisy_chain_impl(fargs, std::forward<Sargs>(sargs)...);
}
template <std::size_t I, typename Ret, typename T, typename... Qargs>
typename std::enable_if<sizeof...(Qargs)+1 == I, Ret>::type
get_last_n(T && t, Qargs && ...qargs)
{
return Ret{std::forward<T>(t), std::forward<Qargs>(qargs)...};
}
template <std::size_t I, typename Ret, typename T, typename... Qargs>
typename std::enable_if<sizeof...(Qargs)+1 != I, Ret>::type
get_last_n(T && , Qargs && ...qargs)
{
static_assert(I <= sizeof...(Qargs) + 1, "Not enough parameters to pass to the singal function");
return get_last_n<I, Ret>(std::forward<Qargs>(qargs)...);
}
template <typename T, typename... Fargs,
typename... Qargs>
void test_signal_daisy_chain(T* t, void(T::*t_signal)(Fargs...),
Qargs&&... qargs)
{
static_assert((sizeof...(Qargs) - sizeof...(Fargs)) % 2 == 0,
"Expecting even number of parameters for object-signal pairs");
auto fargs = get_last_n<sizeof...(Fargs), std::tuple<Fargs...>>(
std::forward<Qargs>(qargs)...);
test_signal_daisy_chain_impl(fargs, t, t_signal,
std::forward<Qargs>(qargs)...);
}
编辑2
可以通过将所有参数存储在元组中来避免运行时递归。下面的test_signal_daisy_chain_flat()
正是这样做的,同时保留与test_signal_daisy_chain()
相同的接口:
template <typename Fargs, typename Pairs, std::size_t ...I>
void apply_pairs(Fargs && fargs, Pairs && pairs, const indexes<I...> &)
{
int dummy[] = {
(apply_method(std::forward<Fargs>(fargs),
std::get<I*2>(pairs),
std::get<I*2+1>(pairs)),
0)...
};
(void)dummy;
}
template <typename T, typename... Fargs,
typename... Qargs>
void test_signal_daisy_chain_flat(T* t, void(T::*t_signal)(Fargs...),
Qargs&&... qargs)
{
static_assert((sizeof...(Qargs) - sizeof...(Fargs)) % 2 == 0,
"Expecting even number of parameters for object-signal pairs");
auto fargs = get_last_n<sizeof...(Fargs), std::tuple<Fargs...>>(
std::forward<Qargs>(qargs)...);
std::tuple<T*, void(T::*)(Fargs...), const Qargs&...> pairs{
t, t_signal, qargs...};
apply_pairs(fargs, pairs,
typename make_indexes<(sizeof...(Qargs) - sizeof...(Fargs))/2>
::type{});
}
注意事项:
- 不断言参数对是否匹配。编译器只是在递归中失败了。
- 传递给函数的参数类型是从第一个函数的签名中推导出来的,而不考虑后续参数的类型 - 后续参数将被转换为所需的类型。
- 所有函数都需要具有相同的签名。
Sargs
与Fargs
分隔开? - biplltest_signal_daisy_chain(u, u_signal, sargs..., fargs...)
调用它。事后看来,我可能需要在我的参数中声明F f, Fargs... fargs
,以便我的扩展正常工作。 - jfhvoid test(T *t, void (T::*t_signal)(Fargs...), U*u, void (U::*u_signal)(Fargs...), Args... args)
,然后将Args
打包到类型元组中,并在此基础上提取Sargs
类型(通过从末尾截断Fargs
)和其他对象-信号对(如果有的话)。当然,如果您计划进行任何重载,则这种方法将不起作用。 - Kuba hasn't forgotten Monicamethod(Object, ptr, Object, ptr, .../* variable amount of "Object, ptr", Fargs...)
的风格,并且