About

An implementation of an interface that declares an observable must implement the behaviour of the observable. The observable must be initiated, freed and invoked.

Implementation

To implement basic observable functionality an implementation must include a maxon::ObserverObjectClass object with MAXON_COMPONENT().

The observable declared with MAXON_OBSERVABLE() is available as a member variable with the defined name and a "_" prefix.

// This example shows an implementation of an interface.
// It implements also an observable that is invoked when the function Ping() is called.
 
class ObserveMeImpl : public maxon::Component<ObserveMeImpl, ObserveMeInterface>
{
  // use ObserverObjectClass to implement basic observer functionality
  MAXON_COMPONENT(NORMAL, maxon::ObserverObjectClass);
 
public:
  // implement observable
  MAXON_OBSERVABLE_IMPL(ObservablePing);
 
  maxon::Result<void> InitComponent()
  {
    iferr_scope;
 
    _count = 0;
 
    // init observable
    _ObservablePing.Init(self, maxon::Id("ObservablePing")) iferr_return;
 
    return maxon::OK;
  }
 
  void FreeComponent()
  {
    // free observable
    _ObservablePing.Free();
  }
 
  MAXON_METHOD void Ping()
  {
    // increment
    ++_count;
 
    // notify subscribers
    iferr (_ObservablePing.Notify(_count))
    {
      DiagnosticOutput("Observable error: @", err);
    }
  }
 
private:
  maxon::Int32 _count;  
};

The observable must be implemented using MAXON_OBSERVABLE_IMPL().

When the component is initiated, also an observable must be initiated with maxon::ObservableBaseInterface::Init().
When the component is freed, the observable must be freed with maxon::ObservableBaseInterface::Free().
The listeners of the observable are called with maxon::ObservableBaseInterface::Notify().

ObservableBaseInterface

Observables are based on maxon::ObservableBaseInterface:

maxon::ObservableBaseInterface::Init(): Has to be called in the implementation's InitComponent() function.
maxon::ObservableBaseInterface::GetObservableId(): Returns the ID defined with Init().
maxon::ObservableBaseInterface::GetOwner(): Gets the owner of the observable.
maxon::ObservableBaseInterface::Free(): Has to be called in the implementation's FreeComponent() function.

Subscriber notification:

maxon::ObservableBaseInterface::Notify(): Send a notification to all subscribers.
maxon::ObservableBaseInterface::SetInverseNotification(): Set true to Notify() in inverse order.

Observers are handled with:

maxon::ObservableBaseInterface::AddObserver(): Add a subscriber to the observable.
maxon::ObservableBaseInterface::RemoveObserver(): Remove an observer from the subscriber list.
maxon::ObservableBaseInterface::GetObserverCount(): Returns the number of observers.

Table of Contents

About

Implementation

ObservableBaseInterface

Further Reading