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https://issues.apache.org/jira/browse/WICKET-1968?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Igor Vaynberg resolved WICKET-1968.
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Resolution: Won't Fix
Assignee: Igor Vaynberg
you can use composition to extend the propertymodel functionality instead of
inheritance
> PropertyModel not easily extendable
> -----------------------------------
>
> Key: WICKET-1968
> URL: https://issues.apache.org/jira/browse/WICKET-1968
> Project: Wicket
> Issue Type: Bug
> Components: wicket
> Affects Versions: 1.4-RC1
> Reporter: Mathieu Carbou
> Assignee: Igor Vaynberg
>
> We wanted to create a LodableDetacheableProeprtyModel like this:
> public abstract class DetachablePropertyModel<T> extends PropertyModel<T> {
> public DetachablePropertyModel(String expression) {
> super(new LoadableDetachableModel<Object>() {
> protected Object load() {
> return DetachablePropertyModel.this.load();
> }
> }, expression);
> }
> protected abstract Object load();
> }
> But this is not possible. Since we cannot access a method of a not yest
> instanciated class.
> So we wanted to chang to this:
> public abstract class DetachablePropertyModel<T> extends PropertyModel<T> {
> public DetachablePropertyModel(String expression) {
> super();
> setChainedModel(new LoadableDetachableModel<Object>() {
> protected Object load() {
> return DetachablePropertyModel.this.load();
> }
> });
> }
> protected abstract Object load();
> }
> But the constructor of AbstractPropertyModel requires a model and also (and
> here is the issue) check for null argument:
> public AbstractPropertyModel(final Object modelObject)
> {
> if (modelObject == null)
> {
> throw new IllegalArgumentException("Parameter
> modelObject cannot be null");
> }
> target = modelObject;
> }
> So the only way to bypass this was to call the super constructor like this:
> public abstract class DetachablePropertyModel<T> extends PropertyModel<T> {
> public DetachablePropertyModel(String expression) {
> super(expression, expression);
> setChainedModel(new LoadableDetachableModel<Object>() {
> protected Object load() {
> return DetachablePropertyModel.this.load();
> }
> });
> }
> protected abstract Object load();
> }
> By giving the expression to the super class, and giving the expression also
> as the object, it works. But it is not correct...
> I think a redesign of AbstractPropertyModel would be necessary: to use the
> method setChainedModel on AbstractPropertyModel , we currently need to first
> have the object instanciated with a non null model.... Which is not what we
> may want...
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