# ComhandleFieldRef.java

    /*
    ** Module   : ComhandleFieldRef.java
    ** Abstract : Data wrapper which associates with a DMO property and provides direct access to
    **            this property.
    **
    ** Copyright (c) 2018-2020, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ---------------------------------Description----------------------------------
    ** 001 CA  20180511 Created initial version.
    ** 002 OM  20200325 Moved to com.goldencode.p2j.util package.
    */

    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.util;

    import com.goldencode.p2j.comauto.ComObject;
    import com.goldencode.p2j.persist.*;

    /**
     * Data wrapper which associates with a DMO property and provides direct access to this property.
     * <p>
     * All writing is done to both the DMO and the local {@link comhandle}'s private {@code value}.
     * On instantiation, the current field value is saved in the {@link comhandle}'s private
     * {@code value}, and this instance will be used for reading until {@link #assign} or
     * {@link #setUnknown} is called again.
     * <p>
     * This usage is OK
     */
    public class ComhandleFieldRef
    extends comhandle
    {
       /** The field referenced by this instance. */
       private final FieldReference fieldRef;

       /**
        * Constructor.
        *
        * @param   dmo
        *          Proxy for record whose field is being accessed.
        * @param   property
        *          Name of dmo field.
        */
       public ComhandleFieldRef(DataModelObject dmo, String property)
       {
          this.fieldRef = new FieldReference(dmo, property);

          RecordBuffer rb = ((BufferReference) dmo).buffer();
          // initialize this instance based on the current buffer state; if no record is loaded in the
          // buffer, then set it to unknown. there will be a 142 - Unable to update field error raised
          // when we try to assign a new value to this instance.
          if (rb.getCurrentRecord() != null)
          {
             super.assign(((comhandle) fieldRef.get()).getResource());
          }
          else
          {
             super.setUnknown();
          }
       }

       /**
        * Modify the contained data of the instance to copy the instance data from the given instance.
        * Generally, the class of the given instance must match the class upon which the
        * {@code assign} method is called, although this is not a strict requirement.
        * <p>
        * Also updates the {@link #fieldRef} with the new state of this comhandle instance.
        *
        * @param   value
        *          The backup instance from which to copy data.
        */
       @Override
       public void assign(Undoable value)
       {
          super.assign(value);

          fieldRef.set(this);
       }

       /**
        * Dedicated assignment method for loading a {@code ComObject} into this {@code comhandle}.
        * This method is only called by {@link com.goldencode.p2j.comauto.ComServer#create}. Stores
        * a newly created {@code ComObject} into this handle.
        * <p>
        * Also updates the {@link #fieldRef} with the new state of this comhandle instance.
        *
        * @param   newVal
        *          The new value to be stored by this handle.
        */
       @Override
       public void assign(ComObject newVal)
       {
          super.assign(newVal);

          fieldRef.set(this);
       }

       /**
        * Sets the state (data and unknown value) of this instance based on the state of the passed
        * instance.
        * <p>
        * Also updates the {@link #fieldRef} with the new state of this comhandle instance.
        *
        * @param    value
        *           The instance from which to copy state.
        */
       @Override
       public void assign(BaseDataType value)
       {
          super.assign(value);

          fieldRef.set(this);
       }

       /**
        * Sets the state of this instance's {@code unknown value} flag or state to {@code true}.
        * <p>
        * <b>Warning: the data stored in this instance may be invalid after calling this method.</b>
        * <p>
        * Also updates the {@link #fieldRef} with the new state of this comhandle instance.
        */
       public void setUnknown()
       {
          super.setUnknown();

          fieldRef.set(this);
       }
    }