Eclipse Platform
Release 3.4

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);
 

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.

Field Summary
static String PROP_NOTIFYING
          The property used to notify any service listeners.
static String RESULT
          A general property that can be used.
 
Method Summary
 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.
 void addEvaluationReference(IEvaluationReference ref)
          Re-add a property change listener that has already been removed by removeEvaluationListener(IEvaluationReference).
 void addServiceListener(IPropertyChangeListener listener)
          When a source change starts recalculating expressions the PROP_NOTIFYING property change is fired with the newValue=Boolean.TRUE.
 IEvaluationContext getCurrentState()
          Get an IEvaluationContext that contains the current state of the workbench application context.
 void removeEvaluationListener(IEvaluationReference ref)
          Remove the listener represented by the evaluation reference.
 void removeServiceListener(IPropertyChangeListener listener)
          Remove the listener for PROP_NOTIFYING property changes.
 void requestEvaluation(String propertyName)
          Request that this service re-evaluate all registered core expressions that contain a property tester for the given property name.
 
Methods inherited from interface org.eclipse.ui.services.IServiceWithSources
addSourceProvider, removeSourceProvider
 
Methods inherited from interface org.eclipse.ui.services.IDisposable
dispose
 

Field Detail

RESULT

public static final String RESULT
A general property that can be used.

See Also:
Constant Field Values

PROP_NOTIFYING

public static final String PROP_NOTIFYING
The property used to notify any service listeners.

See Also:
Constant Field Values
Method Detail

addServiceListener

public 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

public 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

public 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)

addEvaluationReference

public void addEvaluationReference(IEvaluationReference ref)
Re-add a property change listener that has already been removed by removeEvaluationListener(IEvaluationReference).

It will only accept IEvaluationReferences returned from a previous call to addEvaluationListener(Expression, IPropertyChangeListener, String) on this service.

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

Parameters:
ref - The listener to re-add.
See Also:
removeEvaluationListener(IEvaluationReference)

removeEvaluationListener

public void removeEvaluationListener(IEvaluationReference ref)
Remove the listener represented by the evaluation reference.

Parameters:
ref - the reference to be removed.

getCurrentState

public 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

public 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:

Parameters:
propertyName - The fully qualified property name, like org.eclipse.core.resources.name. Must not be null.
Since:
3.4

Eclipse Platform
Release 3.4

Guidelines for using Eclipse APIs.

Copyright (c) Eclipse contributors and others 2000, 2008. All rights reserved.