2.2 KiB
Overview of heterogeneous classes
Description
'CallbackList', 'EventDispatcher', and 'EventQueue' are homogeneous. All listeners must have the same prototype. For example,
eventpp::EventDispatcher<int, void ()> dispatcher;
dispatcher.appendListener(3, []() {}); // OK
dispatcher.appendListener(3, [](std::string) {}); // wrong, can't listen for void(std::string)
There are heterogeneous counterparts, 'HeterCallbackList', 'HeterEventDispatcher', and 'HeterEventQueue'. These classes allow listeners having different prototypes. For example,
eventpp::HeterEventDispatcher<int, eventpp::HeterTuple<void (), void (std::string)> > dispatcher;
dispatcher.appendListener(3, []() {}); // OK
dispatcher.appendListener(3, [](std::string) {}); // OK
Usage
Headers
eventpp/hetercallbacklist.h
eventpp/hetereventdispatcher.h
eventpp/hetereventqueue.h
Template parameters
template <
typename PrototypeList,
typename Policies = DefaultPolicies
>
class HeterCallbackList;
template <
typename Event,
typename PrototypeList,
typename Policies = DefaultPolicies
>
class HeterEventDispatcher;
template <
typename Event,
typename PrototypeList,
typename Policies = DefaultPolicies
>
class HeterEventQueue;
For comparison, below are the template parameters for the homogeneous counterparts
template <
typename Prototype,
typename Policies = DefaultPolicies
>
class CallbackList;
template <
typename Event,
typename Prototype,
typename Policies = DefaultPolicies
>
class EventDispatcher;
template <
typename Event,
typename Prototype,
typename Policies = DefaultPolicies
>
class EventQueue;
The only difference is the Prototype in homo-classes becomes PrototypeList in heter-classes.
In the homo-classes, Prototype is a single function type such as void ().
In the heter-classes, PrototypeList is a list of function types in eventpp::HeterTuple, such as eventpp::HeterTuple<void (), void (std::string), void (int, int)>.
Note: Ideally it would be better to use std::tuple instead of eventpp::HeterTuple, but the problem is that the tuple is instantiated in HeterEventDispatcher which cause compile error that function type can't be instantiated.