content: /*
   *  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.causeway.core.metamodel.services.objectlifecycle;
  
  /**
   *
   * @since 2.0
   *
   */
  public enum PropertyValuePlaceholder {
  
      /**
       * Indicates that the audit trail was unable to determine the value of the property, possibly because an
       * exception was thrown.
       *
       * <p>
       *     One way this can happen is if the property is derived but its implementation does not guard against
       *     null references to other related objects.  In particular, this could occur when deleting an aggregate root
       *     that surfaces the properties of its child entity items directly.  The child entity is deleted first, and
       *     then the aggregate root, but attempting to capture the value of this derived property the fails.
       * </p>
       */
      UNKNOWN,
      /**
       * Used as the <i>pre</i> value of a property for an object that is being created.
       */
      NEW,
      /**
       * Used as the <i>post</i> value of a property for an object that has been deleted.
       */
      DELETED
      ;
  
      @Override
      public String toString() {
          return "[" + name() + "]";
      }
  
  }
  