decl.hpp

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#pragma once
 
#include "builder.hpp"
 
namespace flecs {
namespace _ {
 
// Utility to derive event type from function
template  <typename Func, typename U = int>
struct event_from_func;
 
// Specialization for observer callbacks with a single argument
template  <typename Func>
struct event_from_func<Func, if_t< arity<Func>::value == 1>> {
    using type = decay_t<first_arg_t<Func>>;
};
 
// Specialization for observer callbacks with an initial entity src argument
template  <typename Func>
struct event_from_func<Func, if_t< arity<Func>::value == 2>> {
    using type = decay_t<second_arg_t<Func>>;
};
 
template <typename Func>
using event_from_func_t = typename event_from_func<Func>::type;
 
}
}