Purpose

Sensor is a Header only Library.
It simulates a third party component to be buyed in the context of the make or buy decision.
right click and save link as...: download model to be imported in Enterprise Architect.

This component simulates a sensor that communicates with a Hardware Sensor.
To simulate the Hardware Event just call externalSignal().

Observer Pattern

The communication with the sensor is based on the Observer Pattern.
The Observer is called SensorListener in reference to the java API.

Policy Based Design

The management of the observers is based on "Policy Based Design" according to Alexandrescu, a static variant of the strategy pattern.
Sensor inherits in this design from its template parameter ObserverPolicy:
template<class ObserverPolicy> class Sensor:public ObserverPolicy {..}.
With this technique, the interface of the sensor is extended by the interface of the ObserverPolicy and is available to the clients.

Two policies are provided for the ObserverPolicy:

• The ListenerSingleRawPointerPolicy manages one listener as a native pointer SensorListener*.
• The ListenerMultiple policy manages a list of listeners either as native pointer SensorListener* or as std::weak_ptr<SensorListener>.
  The type is passed to the policy as a template argument.

An ObserverPolicy must meet two conditions: a default constructor and an accessible (protected) fireTrigger(unsigned long timestamp) method.

Examples and Implementation

Examples can be found in main.cpp in demoSingleRawPointer(), in demoMultipleRawPointer() and in demoMultipleSmartPointer().
The Implementations can be found in include/Sensor Sensor.h and in ListenerSingleRawPointer.h and in ListenerMultiple.h