Package org.eclipse.ui.services

Interface IEvaluationService

  • All Superinterfaces:
    IDisposable, IServiceWithSources
    public interface IEvaluationService
extends IServiceWithSources
    Evaluate a core expression against the workbench application context and report updates using a Boolean property. Clients supply an IPropertyChangeListener that will be notified as changes occur.

    This can be used to implement core expressions in client extension points similar to the <enabledWhen> of org.eclipse.ui.handlers/handler elements.

    The service will fire Boolean.TRUE and Boolean.FALSE for the oldValue and newValue in the property change events.

    Adding the evaluation listener will fire one change with oldValue=null and newValue="evaluated expression". Remove the IEvaluationReference will fire one change with oldValue="last evaluated value" and newValue=null.

    Adding a service listener will fire the PROP_NOTIFYING property change event with newValue=Boolean.TRUE when a source change causes expression evaluations to update and another PROP_NOTIFYING property change event with newValue=Boolean.FALSE when the changes that started with a specific source change have finished. The PROP_NOTIFYING change events will not be fired for source changes caused by the outer most recalculations.

    Variable sources can be provided to this service using the org.eclipse.ui.services Extension Point. This makes the available to <with/> expressions.

    This service can be acquired from your service locator: 

     IEvaluationService service = (IEvaluationService) getSite().getService(IEvaluationService.class);
    • This service is available globally.
    Since:
    3.4
    Restriction:
    This interface is not intended to be implemented by clients.
    Restriction:
    This interface is not intended to be extended by clients.

    • Method Detail

      • addServiceListener

        void addServiceListener​(IPropertyChangeListener listener)
        When a source change starts recalculating expressions the PROP_NOTIFYING property change is fired with the newValue=Boolean.TRUE. This property is not fired for any source changes caused by the outer recalculations.

        Note: listeners should be removed when no longer necessary. If not, they will be removed when the IServiceLocator used to acquire this service is disposed.

        Parameters:
        listener - The listener to be notified. Must not be null. Has no effect if the listener has already been added.

      • removeServiceListener

        void removeServiceListener​(IPropertyChangeListener listener)
        Remove the listener for PROP_NOTIFYING property changes.
        Parameters:
        listener - The listener to remove. Must not be null. Has no effect if the listener is not currently registered.

      • addEvaluationListener

        IEvaluationReference addEvaluationListener​(Expression expression,
                                           IPropertyChangeListener listener,
                                           String property)
        Add a listener that can be notified when the workbench application context causes the expression evaluation value to change.

        Note: listeners should be removed when no longer necessary. If not, they will be removed when the IServiceLocator used to acquire this service is disposed.

        Parameters:
        expression - the core expression to evaluate.
        listener - the listener to be notified.
        property - the property contained in the notification
        Returns:
        a token that can be used to remove this listener. removeEvaluationListener(IEvaluationReference)

      • removeEvaluationListener

        void removeEvaluationListener​(IEvaluationReference ref)
        Remove the listener represented by the evaluation reference.
        Parameters:
        ref - the reference to be removed.

      • getCurrentState

        IEvaluationContext getCurrentState()
        Get an IEvaluationContext that contains the current state of the workbench application context. This context changes with the application state, but becomes invalid when the global current selection changes.

        Note: This context should not be modified.

        Returns:
        the latest context.
        See Also:
        ISources.ACTIVE_CURRENT_SELECTION_NAME

      • requestEvaluation

        void requestEvaluation​(String propertyName)
        Request that this service re-evaluate all registered core expressions that contain a property tester for the given property name. This will fire a PROP_NOTIFYING property change event to service listeners.

        Notes:

        • the property must be able to return the new value before this re-evaluation is requested
        • limit calls to this method to avoid unnecessary churn
        • A re-evaluation that does not change the value of an expression will not fire a property change event
        Parameters:
        propertyName - The fully qualified property name, like org.eclipse.core.resources.name. Must not be null.
        Since:
        3.4