program PropertyField_02dField_01;

{$APPTYPE CONSOLE}

uses
  mormot.core.json,
  mormot.core.rtti,
  mormot.orm.core;

type
  TSource = class(TSynAutoCreateFields)
  private
    FField_01: UTF8String;
    FField_02: UTF8String;
  published
    property Field_01: UTF8String read FField_01 write FField_01;
    // even though unused in sample, the prop is needed to force error
    property Field_02: UTF8String read FField_02 write FField_02;
  end;

  TDestination = class(TOrm)
  private
    FDestProp: UTF8String;
  published
    property DestProp: UTF8String read FDestProp write FDestProp;
  end;

var
  Source: TSource;
  Dest: TDestination;
  SourceRtti, DestRtti: TRttiCustom;
  SourceProp, DestProp: PRttiCustomProp;

  CopyData: TRttiVarData;
begin
  // register classes
  DestRtti := Rtti.RegisterClass(TSource);
  SourceRtti := Rtti.RegisterClass(TDestination);

  // get source and dest props
  SourceProp := DestRtti.Props.Find('Field_01');
  DestProp := SourceRtti.Props.Find('DestProp');

  // check them
  Writeln('PropSource ', SourceProp^.Name);
  Writeln('PropDest ', DestProp^.Name);

  // create source
  Source := TSource.Create;
  try
    // and prepare

    // Note: If you put something into Field_01, everything works as expected
    //       it seems to be the empty string, that causes the trouble
    Source.Field_01 := '';
    Source.Field_02 := '';

    // create dest
    Dest := TDestination.Create;
    try
      // read source value
      SourceProp^.GetValue(Source, CopyData);

      Writeln(CopyData.VType);
      // CopyData.VType will be   256/0x0100 for empty string
      // CopyData.VType will be 16640/0x4100 for non-empty string

      // write to dest - EXCEPTION on empty string value

      // Note: I have tried both for "andclear", true and false
      //       without seeing a difference
      DestProp^.SetValue(Dest, CopyData, False);

      // write content of dest
      Writeln('Destination.DestProp _', Dest.DestProp, '_');
    finally
      Dest.Free;
    end;
  finally
    Source.Free;
  end;
end.