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c++referenceobserver-pattern

Reference to Observed class as member variable of the Observer in C++

I'm implementing an Observer pattern in C++. The observer objects need to access to member variables of the Observed class when they are notified. By now I've solved this thing adding a reference to the Observed class as a member variable of the Observer as follows:

class Observer{
     public:   
     Observer(const Observable& obs) : observed_(obs){}
     void notify(const Event& event){
         // get Observable member and do stuff
     }
     private:
     const Observable& observed_;
}
class Observable{

      public:
      void notify(const Event& event){
           //observer list.notify
      }

}

Is the reference a good way for this pattern or is better to use other strategies?

Solution

  • I'd recommend in this case having the Observable instance sent as a member of Event, this way an Observer can watch more than one object, and you also achieve loose coupling between the two classes.