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.

Note: Clients should not extend or implement this interface.

Since:

3.4

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:

• 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