001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *
010 *        http://www.apache.org/licenses/LICENSE-2.0
011 *
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License.
018 */
019
020package org.apache.isis.core.metamodel.interactions;
021
022import org.apache.isis.applib.events.ValidityEvent;
023import org.apache.isis.core.metamodel.facetapi.Facet;
024import org.apache.isis.core.metamodel.facetapi.FacetAbstract.Validating;
025
026/**
027 * Mix-in interface for {@link Facet}s that can advise as to whether a proposed
028 * value is valid.
029 * 
030 * <p>
031 * For example, <tt>MaxLengthFacet</tt> does constrain the length of candidate
032 * values, whereas <tt>DebugFacet</tt> or <tt>MemberOrderFacet</tt> do not -
033 * they are basically just UI hints.
034 * 
035 * @see DisablingInteractionAdvisor
036 * @see HidingInteractionAdvisor
037 */
038public interface ValidatingInteractionAdvisor extends InteractionAdvisorFacet, Validating {
039
040    /**
041     * Whether the validation represented by this facet passes or fails.
042     * 
043     * <p>
044     * Implementations should use the provided {@link ValidityContext} to
045     * determine whether they declare the interaction invalid. They must however
046     * guard against a <tt>null</tt> {@link ValidityContext#getTarget() target}
047     * and {@link ValidityContext#getSession() session} - neither are guaranteed
048     * to be populated.
049     */
050    String invalidates(final ValidityContext<? extends ValidityEvent> ic);
051}