/**
* Copyright 2014 55 Minutes (http://www.55minutes.com)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package fiftyfive.wicket.list;
import java.util.List;
import org.apache.wicket.markup.html.list.ListView;
import org.apache.wicket.model.IModel;
/**
* A {@link ListView} that returns <code>false</code> for {@link #isVisible}
* if its list is empty. This allows you to use
* the <code><wicket:enclosure></code> tag to hide surrounding markup.
* Therefore you can use this component to ensure that, for example,
* the <code><ul></code> is ommitted when you have zero
* <code><li></code> elements.
* <em>This is necessary for valid XHTML markup.</em>
* <p>
* Example usage:
* <pre class="example">
* <wicket:enclosure child="item">
* <ul>
* <li wicket:id="item">...</li>
* </ul>
* </wicket:enclosure>
*
* add(new ConditionalListView<Person>("people", personList) {
* @Override protected void populateItem(ListItem<Person> item)
* {
* item.add(...);
* }
* });</pre>
* <p>
* In this example, if the {@code personList} model is {@code null} or empty,
* the entire enclosure will be omitted from the HTML output.
*/
public abstract class ConditionalListView<T> extends ListView<T>
{
public ConditionalListView(String id)
{
super(id);
}
public ConditionalListView(String id,
IModel<? extends List<? extends T>> model)
{
super(id, model);
}
public ConditionalListView(String id, List<? extends T> list)
{
super(id, list);
}
/**
* Returns <code>false</code> if the list is empty.
*/
@Override
public boolean isVisible()
{
return getViewSize() > 0;
}
}