Edit

Lifecycle Callbacks

The lifecycle callbacks are used to allow the user to run custom code when the component is constructed or disposed. The @PreDispose and @PostDispose API documentation describes the behaviour and requirements in detail. Methods annotated with @PostConstruct are invoked after the arez components constructor has been invoked and after all the reactive elements (i.e. the ObservableValue, Observer and ComputableValue instances) have been created and any @Observe have been scheduled but before any the scheduler has been triggered and thus before any observers have been executed for the first time.

The lifecycle callbacks are typically used to integrate with the native platform. On the web platform, the lifecycle methods are often used to add and remove event listeners so that the Arez component can update Arez state when an event occurs.

Below is an example that was extracted from a reactive component that exposed the "hash" part of the url as reactive state.

@ArezComponent
public abstract class BrowserLocation
{
  private final HashChangeEventListener _listener = this::onHashChangeEvent;
  ...

  @PostConstruct
  void postConstruct()
  {
    WindowGlobal.addHashchangeListener( _listener, false );
    ...
  }

  @PreDispose
  void preDispose()
  {
    WindowGlobal.removeHashchangeListener( _listener, false );
  }

  ...
}