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Search found 8 results on 1 pages for 'tdataset'.

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• Database application using MVC paradigm

  - by Andrei K.

  In classic Delphi database application we have a form, a set of data-aware visual controls connected to TDataSets via TDataSources. If one wants to design database application using MVC model, where to place TDataSet components? Should they stay on form and therefore be a part of View? Or should they be encapsulated inside some Model object? If the latter how they could be bound to visual components?

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• Return no records if FIndKey results in False?

  - by jwilfong

  Using TDataSet.FindKey you can locate records. When it results in True the datasets cursor will be positioned on the found record. When it results in False the cursor is not moved. This results in the record data prior to FindKey being issued being displayed in data aware components. How can I code the result of FindKey to return an empty record? if Not tblSomeTable.FindKey([SomeSearchData]) then begin < code to return empty or move data cursor to neutral position > end; Thanks, John

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• Improve speed of own debug visualizer for Delphi 2010

  - by netcodecz

  I wrote Delphi debug visualizer for TDataSet to display values of current row, source + screenshot: http://delphi.netcode.cz/text/tdataset-debug-visualizer.aspx . Working good, but very slow. I did some optimalization (how to get fieldnames) but still for only 20 fields takes 10 seconds to show - very bad. Main problem seems to be slow IOTAThread90.Evaluate used by main code shown below, this procedure cost most of time, line with ** about 80% time. FExpression is name of TDataset in code. procedure TDataSetViewerFrame.mFillData; var iCount: Integer; I: Integer; // sw: TStopwatch; s: string; begin // sw := TStopwatch.StartNew; iCount := StrToIntDef(Evaluate(FExpression+'.Fields.Count'), 0); for I := 0 to iCount - 1 do begin s:= s + Format('%s.Fields[%d].FieldName+'',''+', [FExpression, I]); // FFields.Add(Evaluate(Format('%s.Fields[%d].FieldName', [FExpression, I]))); FValues.Add(Evaluate(Format('%s.Fields[%d].Value', [FExpression, I]))); //** end; if s<> '' then Delete(s, length(s)-4, 5); s := Evaluate(s); s:= Copy(s, 2, Length(s) -2); FFields.CommaText := s; { sw.Stop; s := sw.Elapsed; Application.MessageBox(Pchar(s), '');} end; Now I have no idea how to improve performance.

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• Adding a calculated field to a Query at run time.

  - by JamesB

  I'm getting data using a query in Delphi, and would like to add a calculated field to the query before it runs. The calculated field is using values in code as well as the query so I can't just calculate it in SQL. I know I can attach an OnCalcFields Event to actually make the calculation, but the problem is after adding the calculated field there are no other fields in the query... I did some digging and found that all of the field defs are created but the actual fields are only created if DefaultFields then CreateFields Default Fields is specified procedure TDataSet.DoInternalOpen; begin FDefaultFields := FieldCount = 0; ... end; Which would indicate that if you add fields you only get the fields you added. I would like all the fields in the query AS WELL AS the ones I Add. Is this possible or do I have to add all the fields I'm using as well?

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• Crosstab/Cube/Pivot Components for Delphi

  - by Anagoge

  I'm looking for a Delphi VCL crosstab/cube/pivotcube/olap grid component for Delphi 2009, 2010, or XE. I'm willing to sacrifice advanced features to get something open/free (or very cheap if I must) to make it easier to collaborate with any future developers without anyone having to purchase more components than I already use, since this will just be used in one screen. If there isn't anything appropriate out there, I may try to implement something simple on my own. I can live with some fairly basic features: drag and drop to configure dimensions, sort by a column, allow totals/min/max for a column, and (optionally) expand/collapse or drill down to sub-categories. Blazing performance and enterprise scalability are not required, since there should be less than 2000 source rows. There appear to be several decent options in the commercial space (ExpressPivotCube, FastCube, HierCube), but they are all a few hundred dollars. This project already uses existing installations of Excel 2007 and SQL Server 2005/2008, so I might consider leveraging those, though I'd prefer a native Delphi component, if possible. There are also the very old Decision Cube components included in Delphi's Source\xtab directory, but they apparently no longer support unicode compilers (Delphi 2009+), since I got dozens of unicode-related compilation errors while test compiling that source in Delphi XE. Those components also still link to the long-deprecated BDE! Has anyone modified Decision Cube to support unicode/pure-TDataSet? The online tutorials I found were incomplete and silent on the dozens of BDE/unicode compilation errors I see, so I might have to tackle that on my own. Does anyone have suggestions where to start for a free/cheap basic crosstab/pivot grid component?

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• Do I have to allocate and free records when using TList<T> in Delphi?

  - by afrazier

  The question more or less says it all. Given the following record structure: type TPerson = record Name: string; Age: Integer; end; PPerson = ^TPerson; TPersonList = TList<TPerson>; Is the following code valid? procedure ReadPeople(DataSet: TDataSet; PersonList: TPersonList); begin PersonList.Count := DataSet.RecordCount; if DataSet.RecordCount = 0 then Exit; DataSet.First; while not DataSet.Eof do begin PersonList[DataSet.RecNo].Name := DataSet.FieldByName('Name').AsString; PersonList[DataSet.RecNo].Age := DataSet.FieldByName('Age').AsInteger; DataSet.Next; end; end; Do I have to use GetMem/FreeMem to allocate and free records an instance of TPersonList, or am I free to directly access the TPersonList entries directly? My gut says that the code should be valid, though I'm not sure if there's any wrinkles related to record initialization or finalization.

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• Correct Delphi compiler switches to stop in the user's code, not my component's

  - by Jeremy Mullin

  I'm modifying our VCL components so the end user's application links to our dcu files, instead of building our source code each time. We have everything working, but I want the debugger to stop on the user's code when an exception is raised. At first it would stop in our dcu and open the CPU window. I was able to prevent that by removing debug info from the dcu files. But now it still doesn't stop in the users code (like DevExpress libraries and others do). The following screencast is a short example. The first time I cause an exception in the DevExpress code, and the debugger correctly stops in my button event. The second time I cause an exception in my components, but the debugger doesn't have my button event on the call stack, and doesn't show me where the problem was. Any ideas why? http://screencast.com/t/NjhlOTRk Currently building the DCU's with these options: -$W+ -$D- -h -w -q Update: The TDataSet methods in between my component and the button event seem to cause this behavior. If I instead call a direct method of my table, I get the expected behavior. I'm guessing there isn't anything I can do about this, but I'm still curious why it happens.

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• Mysterious double execution of Click handler after change to Windows 2008 Server

  - by mjn

  After moving a Delphi 2009 application from a Windows 2003 / Citrix environment to a 64 bit Windows 2008 R2 environment (users now use RDP instead of Citrix), there are frequent runtime errors which are caused by a double exection of a menu item click handler. The first call of the event handler opens a modal form. Then the same event handler is triggered again and thus a runtime exception occurs since the visible form can not be made modal. The madExcept stack trace looks like this: main thread ($2dc): 004ffa88 +06c Ladelist.exe Forms TCustomForm.ShowModal 0052f4ff +0bb Ladelist.exe DB TDataSet.SetActive 008fc9a1 +089 Ladelist.exe u_ladeli 928 +16 TForm1.EditLoadingList 008fadec +070 Ladelist.exe u_ladeli 504 +5 TForm1.OpenLoadingListClick <----- 2 004d6e27 +0a7 Ladelist.exe Menus TMenuItem.Click 004d857f +0ef Ladelist.exe Menus DoClick 004d866b +087 Ladelist.exe Menus TMenu.IsShortCut 005001c1 +04d Ladelist.exe Forms TCustomForm.IsShortCut 004e8dc0 +068 Ladelist.exe Controls TWinControl.IsMenuKey 004e8f89 +011 Ladelist.exe Controls TWinControl.CNSysKeyDown 004e247e +2d2 Ladelist.exe Controls TControl.WndProc 004e6983 +513 Ladelist.exe Controls TWinControl.WndProc 004fb5e8 +594 Ladelist.exe Forms TCustomForm.WndProc 004e20a4 +024 Ladelist.exe Controls TControl.Perform 004856e0 +014 Ladelist.exe Classes StdWndProc 004e609c +02c Ladelist.exe Controls TWinControl.MainWndProc 004856e0 +014 Ladelist.exe Classes StdWndProc 775b00e3 +02b ntdll.dll KiUserCallbackDispatcher 008fc9a1 +089 Ladelist.exe u_ladeli 928 +16 TForm1.EditLoadingList 008fadec +070 Ladelist.exe u_ladeli 504 +5 TForm1.OpenLoadingListClick <----- 1 004d6e27 +0a7 Ladelist.exe Menus TMenuItem.Click 004d857f +0ef Ladelist.exe Menus DoClick 004d866b +087 Ladelist.exe Menus TMenu.IsShortCut 005001c1 +04d Ladelist.exe Forms TCustomForm.IsShortCut 004e8dc0 +068 Ladelist.exe Controls TWinControl.IsMenuKey 004e8e0d +01d Ladelist.exe Controls TWinControl.CNKeyDown 004e247e +2d2 Ladelist.exe Controls TControl.WndProc 004e6983 +513 Ladelist.exe Controls TWinControl.WndProc 004fb5e8 +594 Ladelist.exe Forms TCustomForm.WndProc 004e20a4 +024 Ladelist.exe Controls TControl.Perform 004e609c +02c Ladelist.exe Controls TWinControl.MainWndProc 004856e0 +014 Ladelist.exe Classes StdWndProc 775b00e3 +02b ntdll.dll KiUserCallbackDispatcher 753c3675 +010 kernel32.dll BaseThreadInitThunk

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