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.

Member functions and types

The heter-classes have similar functions and types as the homo-classes. The major difference is, in the homo-classes, listeners can have only one prototype, while in the heter-classes, listeners can have any prototypes which are in the PrototypeList specified in the class template parameters.

2.5 KiB Raw Blame History