Subject: Re: [Boost-users] switch_
From: niXman (i.nixman_at_[hidden])
Date: 2015-09-25 09:25:18
> I see Boost.Switch_ was provisionally accepted back inJan 2008.
> I see some doc here:
> http://dancinghacker.com/switch
> But I can't see it released in recent boost versions
>
> I need to select a type to dynamic_cast to based on a runtime index, so
> I
> would have the type in a mpl::vector, and use the switch_ to pick up
> the
> right type? I have under 20 types.
>
> in pseudo c++11:
>
>
> void f(std::size_t i, const T* obj)
> {
>
> typedef mpl::vector<T0, .... Tn> alltypes_t;
>
> const auto* drvobj = dynamic_cast<...>(obj);
> /// what do I set as arg of dynamic_cast
>
> }
>
> If switch_ can help, where do I get the code for it?
Hi,
You can simply use the 'std::map<std::size_t, void(*)(const void*)>'
like this:
void f(std::size_t i, const void* obj) {
static const std::map<std::size_t, void(*)(const void*)> map = {
{0 , [](const void *obj){ derived0 *p = dynamic_cast<derived0
>(o); ...; }}
,{1 , [](const void *obj){ derived1 *p = dynamic_cast<derived1
>(o); ...; }}
,{2 , [](const void *obj){ derived2 *p = dynamic_cast<derived2
>(o); ...; }}
,{18, [](const void *obj){ derived18 *p =
dynamic_cast<derived18>(o); ...; }}
};
auto it = map.find(i);
assert(it != map.end());
it->second(obj);
}
...
> const auto* drvobj = dynamic_cast<...>(obj);
> /// what do I set as arg of dynamic_cast
In that case the boost::switch_ not help you.