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    
020    package org.apache.isis.core.progmodel.facets.collections.validate;
021    
022    import org.apache.isis.core.metamodel.adapter.ObjectAdapter;
023    import org.apache.isis.core.metamodel.facetapi.Facet;
024    import org.apache.isis.core.metamodel.interactions.ValidatingInteractionAdvisor;
025    
026    /**
027     * Validate that an object can be added to a collection.
028     * 
029     * <p>
030     * In the standard Apache Isis Programming Model, corresponds to invoking the <tt>validateAddToXxx</tt> support method
031     * for a collection.
032     * 
033     */
034    public interface CollectionValidateAddToFacet extends Facet, ValidatingInteractionAdvisor {
035    
036        /**
037         * Reason the object cannot be added, or <tt>null</tt> if okay.
038         */
039        public String invalidReason(ObjectAdapter target, ObjectAdapter proposedArgument);
040    }