Devart Forums

Code: Select all

procedure TMemData.SetToBookmark(Bookmark: PRecBookmark);
...
  if (Bookmark.RefreshIteration = FRefreshIteration) and
    (IntPtr(Bookmark.Item) <> nil)
  then begin
....
  end;

// Set by order
  inherited;
end;

Code: Select all

function TMemData.CompareBookmarks(Bookmark1, Bookmark2: PRecBookmark): integer;
...
    if Bookmark1.RefreshIteration = Bookmark2.RefreshIteration then
      if Bookmark1.Item = Bookmark2.Item then begin
...
        if (IntPtr(Bookmark1.Item) <> nil) and (IntPtr(Bookmark2.Item) <> nil) then
          try // for freed item
            if Bookmark1.Item.Order >= Bookmark2.Item.Order then
              if Bookmark1.Item.Order = Bookmark2.Item.Order then
...
// Compare by order
  Result := inherited CompareBookmarks(Bookmark1, Bookmark2);
end;

Code: Select all

function TMemData.BookmarkValid(Bookmark: PRecBookmark): boolean;
begin
  if IntPtr(Bookmark) <> nil then
    begin
      if (Bookmark.RefreshIteration = FRefreshIteration) and (IntPtr(Bookmark.Item) <> nil) then
        Result := (Bookmark.Item.Order <= FRecordCount)
      else
        Result := (Bookmark.Order <> -1) and (Bookmark.Order <= FRecordCount);
    end
  else
    Result := False;

  if Result and Filtered then
    Result := not OmitRecord(Bookmark.Item);
end;

Code: Select all

procedure TMemData.SetToBookmark(Bookmark: PRecBookmark);
...
  if (Bookmark.RefreshIteration = FRefreshIteration) and
    (IntPtr(Bookmark.Item) <> nil)
  then begin
....
  end;

// Set by order
  inherited;
end;

Code: Select all

  if IntPtr(Bookmark) <> nil then
    Result := ((Bookmark.Order <> -1) and (Bookmark.Order <= FRecordCount)) or
      ((Bookmark.RefreshIteration = FRefreshIteration) and (IntPtr(Bookmark.Item) <> nil) and (Bookmark.Item.Order <= FRecordCount))
  else
    Result := False;

Code: Select all

function TMemData.BookmarkValid(Bookmark: PRecBookmark): boolean;
begin
  if IntPtr(Bookmark) <> nil then
    begin
      // 1. step - RefreshIteration and Item
      if (Bookmark.RefreshIteration = FRefreshIteration) and 
         (IntPtr(Bookmark.Item) <> nil) then
        Result := (Bookmark.Item.Order <= FRecordCount)
      else
        // 2. step - ORDER
        Result := (Bookmark.Order <> -1) and (Bookmark.Order <= FRecordCount);
    end
  else
    Result := False;
end;

Code: Select all

program Project1;

uses
  Forms,
  Unit1 in 'Unit1.pas' {Form1};

{$R *.res}

begin
  Application.Initialize;
  Application.MainFormOnTaskbar := True;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

Code: Select all

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, DB, MemDS, DBAccess, MSAccess;

type
  TForm1 = class(TForm)
    Connection: TMSConnection;
    Query: TMSQuery;
    Button2: TButton;
    Label3: TLabel;
    lPocet2: TLabel;
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

uses
  MemData;

{$R *.dfm}

procedure TForm1.Button2Click(Sender: TObject);

  function __GetQueryStr(PocetZaznamu: integer): string;

    function __RandomChar: string;
    begin
      Result := Chr(65 + Random(26));
    end;

    function __RandomWord(PocetPismen: integer): string;
    var
      i: integer;
    begin
      Result := '';
      for i := 0 to PocetPismen - 1 do
        Result := Result + __RandomChar;
    end;

  var
    i: integer;
  begin
    Randomize;
    Result := 'SELECT * FROM (';
    for i := 0 to PocetZaznamu - 1 do
    begin
      if i = 0 then
        Result := Result +
          Format(
            '(SELECT %d AS Field1, ''%s'' AS Field2, ''%s'' AS Field3, ''%s'' AS Field4)',
            [Random(1000),
             __RandomWord(3),
             __RandomWord(2),
             __RandomWord(1)])
      else
        Result := Result +
          Format(
            '(SELECT %d, ''%s'', ''%s'', ''%s'')',
            [Random(1000),
             __RandomWord(3),
             __RandomWord(2),
             __RandomWord(1)]);
      if i < (PocetZaznamu - 1) then
        Result := Result + ' UNION ALL'#13
    end;
    Result := Result + ') t';
  end;

var
  B: TBookmark;
begin
  Connection.Connect;

  Query.SQL.Text := __GetQueryStr(10);
  Query.Open;

  Query.Last;
  B := Query.Bookmark;

  Query.Close;
  Query.SQL.Text := __GetQueryStr(100);
  Query.Open;

  if Query.BookmarkValid(B) then
    ShowMessage('Ooops, invalid bookmark is valid!');

  lPocet2.Caption := IntToStr(StrToIntDef(lPocet2.Caption, 0) + 1);
  lPocet2.Refresh;
end;

end.

Code: Select all

var
  bm: TBookmark;
begin
  ADOQuery1.SQL.Text := 'select * from table1';
  ADOQuery1.Open;
  bm := ADOQuery1.Bookmark;

  ADOQuery2.SQL.Text := 'select * from table2';
  ADOQuery2.Open;
  if ADOQuery2.BookmarkValid(bm) then // bm is a valid bookmark
    ADOQuery2.GotoBookmark(bm);
end;