wicket-core/src/main/java/org/apache/wicket/markup/html/form/IChoiceRenderer.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.wicket.markup.html.form;

import java.util.List;

import org.apache.wicket.model.IDetachable;
import org.apache.wicket.model.IModel;

/**
 * Renders one choice. Separates the 'id' values used for internal representation from 'display
 * values' which are the values shown to the user of components that use this renderer.
 *
 * @author jcompagner
 *
 * @param <T>
 *            The model object type
 */
public interface IChoiceRenderer<T> extends IDetachable
{
	/**
	 * Get the value for displaying to an end user.
	 *
	 * @param object
	 *            the actual object
	 * @return the value meant for displaying to an end user
	 */
	Object getDisplayValue(T object);

	/**
	 * This method is called to get the id value of an object (used as the value attribute of a
	 * choice element) The id can be extracted from the object like a primary key, or if the list is
	 * stable you could just return a toString of the index.
	 * <p>
	 * Note that the given index can be {@code -1} if the object in question is not contained in the
	 * available choices.
	 *
	 * @param object
	 *            The object for which the id should be generated
	 * @param index
	 *            The index of the object in the choices list.
	 * @return String
	 */
	String getIdValue(T object, int index);

	/**
	 * This method is called to get an object back from its id representation.
	 *
	 * The {@code id} may be used to find/load the object in a more efficient way
	 * than loading all {@code choices} and find the one with the same id in the list
	 *
	 * @param id
	 *          The id representation of the object
	 * @param choices
	 *          The list of all rendered choices
	 * @return A choice from the list that has this {@code id}
	 */
	T getObject(String id, IModel<? extends List<? extends T>> choices);

	/**
	 * Override when needed.
	 */
	@Override
	default void detach()
	{
	}
	
}