org.scopemvc.model.basic
Class BasicModel

java.lang.Object
  |
  +--org.scopemvc.model.basic.BasicModel

All Implemented Interfaces:

ModelChangeEventSource, ModelChangeListener, ModelChangeTypes

Direct Known Subclasses:

ArrayModel, ListModel, ListModelAdaptor, SetModel

public abstract class BasicModel

extends java.lang.Object

implements ModelChangeEventSource, ModelChangeTypes

A simple implementation of ModelChangeEventSource for use as a base class. An alternative (JavaBeans style) is to use ModelChangeEventSupport as a delegate in all models.

To implement a BasicModel:

1. extend BasicModel,
2. Notify interested listeners of changes in Model state at the end of set methods by: fireModelChange(...)
3. Register as a ModelChangeListener with submodels in the appropriate set methods to ensure event propagation up the tree of models. For example:

      public final static Selector NAME = Selector.fromString("name");
      public final static Selector ADDRESS = Selector.fromString("address");
   
      public void setAddress(AddressModel inAddress) throws ModelException {
          if (inAddress == address) {
              return;
          }
        unlistenOldSubmodel(ADDRESS); address =
      inAddress; listenNewSubmodel(ADDRESS);
      fireModelChange(VALUE_CHANGE, ADDRESS); } 

   
   This ensures that any change in the Address's state is received by this parent which will then fire its own ModelChangeEvent to its listeners. See ModelChangeEventSource for more discussion. Note the use of the Selector constants: this is for convenience (and performance).
4. Use Scope's collection models instead of the regular Java collections: Scope collections propagate changes to submodels as above and are compliant ModelChangeEventSources. These collections must be listened to in the same way as other submodel properties. Note that Scope collections are just thin wrappers on native Java collections.

Version:

$Revision: 1.11 $ $Date: 2002/09/12 10:51:03 $

Author:

Steve Meyfroidt

Field Summary

Fields inherited from interface org.scopemvc.core.ModelChangeTypes

ACCESS_CHANGED, VALUE_ADDED, VALUE_CHANGED, VALUE_REMOVED

Constructor Summary

BasicModel()

Method Summary

void	addModelChangeListener(ModelChangeListener inListener) Adds a listener for ModelChangeEvent
void	fireModelChange(int inChangeType, Selector inSelector) Fire a ModelChangeEvent to all listeners
protected void	listenNewSubmodel(Selector inSelector) Convenience for BasicModel implementors: call this at the end of setters for submodel properties (ie properties of type ModelChangeEventSource) to register this as a ModelChangeListener to the current submodel for event propagation.
void	makeActive(boolean inActive) Control whether this BasicModel broadcasts ModelChangeEvents.
void	modelChanged(ModelChangeEvent inEvent) Handle changes to children ModelChangeEventSources by firing a change event from this (and propagating the original Selector).
void	removeModelChangeListener(ModelChangeListener inListener) Removes a listener for ModelChangeEvent
protected void	unlistenOldSubmodel(Selector inSelector) Convenience for BasicModel implementors: call this at the start of setters for submodel properties (ie properties of type ModelChangeEventSource) to deregister this as a ModelChangeListener to the current submodel (about to be set to another Model).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BasicModel

public BasicModel()

Method Detail

addModelChangeListener

public final void addModelChangeListener(ModelChangeListener inListener)

Adds a listener for ModelChangeEvent

Specified by:

addModelChangeListener in interface ModelChangeEventSource

Parameters:

inListener - The listener to be added

removeModelChangeListener

public final void removeModelChangeListener(ModelChangeListener inListener)

Removes a listener for ModelChangeEvent

Specified by:

removeModelChangeListener in interface ModelChangeEventSource

Parameters:

inListener - The listener to be removed

fireModelChange

public final void fireModelChange(int inChangeType,
                                  Selector inSelector)

Fire a ModelChangeEvent to all listeners

Specified by:

fireModelChange in interface ModelChangeEventSource

Parameters:

inChangeType - The type of the change. One of the ModelChangeTypes values

inSelector - The Selector for the property of the model affected by the change

modelChanged

public void modelChanged(ModelChangeEvent inEvent)

Handle changes to children ModelChangeEventSources by firing a change event from this (and propagating the original Selector). If the event's source is no longer a child property of this parent then there is no need to continue propagating the event.

Specified by:

modelChanged in interface ModelChangeEventSource

Parameters:

inEvent - the event received from a child ModelChangeEventSource.

makeActive

public void makeActive(boolean inActive)

Control whether this BasicModel broadcasts ModelChangeEvents. Make sure nested calls are properly matched to fully re-activate a BasicModel that was deactivated.

Subclasses may override this to propagate the activation state to child BasicModel properties if necessary.

Parameters:

inActive - true to activate this model, false to desactivate it

unlistenOldSubmodel

protected final void unlistenOldSubmodel(Selector inSelector)

Convenience for BasicModel implementors: call this at the start of setters for submodel properties (ie properties of type ModelChangeEventSource) to deregister this as a ModelChangeListener to the current submodel (about to be set to another Model).

Parameters:

inSelector - The Selector for the submodel

listenNewSubmodel

protected final void listenNewSubmodel(Selector inSelector)

Convenience for BasicModel implementors: call this at the end of setters for submodel properties (ie properties of type ModelChangeEventSource) to register this as a ModelChangeListener to the current submodel for event propagation.

Parameters:

inSelector - The Selector for the submodel