Question

“How do I store descriptive information with my report template?”

Solution

If you are storing the templates to a database, then you can use the Report.Template.OnSaveEnd and OnLoadEnd events to store and load the custom information to appropriate data fields for the record. (This is the technique used by the ReportExplorer.)

If you are storing templates to .rtm files, then you will need to store the custom information in an Offset area of the template file. The Report.Template object enables you do this by utilizing the Template.Offset property and the Template.OnLoadStart and OnLoadEnd events. Below is a detailed example.

Example:

1. Create a new application.
2. Add to the main form one TButton, one TppReport and one TppDesigner.
3. Set the Designer’s Report property to ppReport1.
4. Add ppTypes to the uses clause.

type
  TForm1 = class(TForm)
    Button1: TButton;
    ppReport1: TppReport;
    ppDesigner1: TppDesigner;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    procedure LoadReportStreamEvent(Sender: TObject; Stream: TStream);
    procedure SaveReportStreamEvent(Sender: TObject; Stream: TStream);

  public

  end;  { class TForm1 }


{note: use compiler directive to declare strings as 'ShortStrings'
       this is required for record structures}

{$H-}

  {record structure used to store information inside report template }
  TmyTemplateInfo = record
      HeaderID: Integer;
      Comments: String;
      DateTime: TDateTime;

  end; {record, TppTemplateRec}

{$H+}


const
  cHeaderID = 12345;

implementation


{-------------------------------------------------}
{ TForm1.FormCreate }

procedure TForm1.FormCreate(Sender: TObject);
begin

  {setup Template events }
  ppReport1.Template.Format      := ftASCII;
  ppReport1.Template.Offset      := SizeOf(TmyTemplateInfo);
  ppReport1.Template.OnLoadStart := LoadReportStreamEvent;
  ppReport1.Template.OnSaveEnd   := SaveReportStreamEvent;

end; {procedure, FormCreate}

{-------------------------------------------------}
{ TForm1.Button1Click }

procedure TForm1.Button1Click(Sender: TObject);
begin

  ppDesigner1.Show;

end; {procedure, Button1Click}

{--------------------------------------------------}
{ TForm1.LoadReportStreamEvent }

procedure TForm1.LoadReportStreamEvent(Sender: TObject; Stream: TStream);
var
  lTemplateInfo: TmyTemplateInfo;
  lsMessage: String;

begin

  {read string stored in template header }
  Stream.Seek(0, soFromBeginning);
  Stream.Read(lTemplateInfo, SizeOf(TmyTemplateInfo));

  {note: if not one of the templates with our header info, then set Offset to 0 }
  if lTemplateInfo.HeaderID = cHeaderID then
    begin
      lsMessage := 'Reading data from template file: ' + #13#10 + #13#10 +
                    lTemplateInfo.Comments + ' (' + DateTimeToStr(lTemplateInfo.DateTime) + ')';

      MessageDlg(lsMessage, mtInformation, [mbOK],0);
      ppReport1.Template.Offset := SizeOf(TmyTemplateInfo);
    end
  else
    ppReport1.Template.Offset := 0;

end; {procedure, LoadReportStreamEvent}


{------------------------------------------------------------------------------}
{ TForm1.SaveReportStreamEvent }

procedure TForm1.SaveReportStreamEvent(Sender: TObject; Stream: TStream);
var
  lTemplateInfo: TmyTemplateInfo;
  lsMessage: String;

begin

  lTemplateInfo.HeaderID := cHeaderID;
  lTemplateInfo.Comments := 'This comment is being stored inside the report template, ' + #13#10 +
              'along with the date and time written. ';
  lTemplateInfo.DateTime := Now;

  {write info to template header}
  Stream.Seek(0, soFromBeginning);
  Stream.Write(lTemplateInfo, SizeOf(TmyTemplateInfo));

  lsMessage := 'Writing data to template file: ' + #13#10 + #13#10 +
                lTemplateInfo.Comments + ' (' + DateTimeToStr(lTemplateInfo.DateTime) + ')';
  MessageDlg(lsMessage, mtInformation, [mbOK],0);

end; {procedure, SaveReportStreamEvent}