Signals (Observer Pattern)

Classes used to implement the observer design pattern. More...

Classes
class	Util::IFunctor< T >
	Interface for functor that wraps a void function with one argument (abstract). More...
class	Util::MethodFunctor< Object, T >
	Functor that wraps a one-argument class member function. More...
class	Util::Signal< T >
	Notifier (or subject) in the Observer design pattern. More...

Detailed Description

Classes used to implement the observer design pattern.

A Signal maintains a list of registered "observers" and "notifies" each observer when Signal::notify() is called, by calling a specific method of each observer object. Observers are stored internally as a list pointers to IFunctor objects, each of which can be called using an overloaded () operator. Each Functor is created as an instance of the MethodFunctor<T>, which stores a pointer to a T object and to pointer to a method of class T, and which uses the () operator to call a specific method of a specific object.

The Signal, IFunctor, and MethodFunctor classes are all templates that take an optional parameter T that represents the typename of of a parameter that should be passed to the notify method of the Signal<T>, which then passes it to the void (const T&) operator of the IFunctor<T>. In each template, setting typename T to the the default value of T=void invokes a explicit specialization in which the void Signal<>::notify() and void IFunctor<>::operator () take no parameters. An instance of Signal<> is thus a signal that notifies observers by calling methods that take no arguments, while a Signal<T> is a signal that notifies observers by calling methods with a signature void (const &T). MethodFunctor takes two template parameters: MethodFunctor<ObserverClass, typename T=void> is a subclass of IFunctor<T> for which the (const T&) operator calls a specific void (const T&) methodof an observer of type class ObserverObject.