boost之signal2

简介

signal2实现了信号槽机制，即事件总线EventBus

signal

信号的模板为

template<
typename Signature, typename Combiner = optional_last_value<typename boost::function_traits<Signature>::result_type>, typename Group = int, typename GroupCompare = std::less<Group>, typename SlotFunction = boost::function<Signature>, typename ExtendedSlotFunction = typename detail::variadic_extended_signature<Signature>::function_type, typename Mutex = signals2::mutex> 
class signal

信号的特例化为

template<
typename Combiner, typename Group, typename GroupCompare, typename SlotFunction, typename ExtendedSlotFunction, typename Mutex, typename R, typename ... Args>
class signal<
R (Args...), Combiner, Group, GroupCompare, SlotFunction, ExtendedSlotFunction, Mutex>

Sinagure：定义函数返回值，参数类型，typename R, typename T1, typename T2, …, typename TN
Combiner：默认值为optional_last_value<函数签名的返回值>
Group：默认值为int
GroupCompare：默认值为less
SlotFunction：默认值为function
ExtenedSlotFunction：默认值为typename detail::extended_signature<function_traits::arity, Signature>::function_type
Mutex：默认值为mutex

signal_impl

connection_list_type：其类型为grouped_list<Group, GroupCompare, connection_body_type>，而connection_body_type类型为shared_ptr<connection_body<group_key_type, slot_type, Mutex>>

SlotType：为slot<R (Args…), SlotFunction>
group_key_type类型为

enum slot_meta_group {front_ungrouped_slots, grouped_slots, back_ungrouped_slots};
template<typename Group>
struct group_key
{typedef std::pair<enum slot_meta_group, boost::optional<Group>> type;
};

slot

slot对于普通函数的特例化为slot<R (Args…), SlotFunction>，其结构为