TVirtualDBData

Virtual data adapter for linking TDataSet or TDataSource to TeeGrid

Overview

TVirtualDBData is a virtual data class that links TDataSet or TDataSource fields to a TeeGrid. It provides automatic integration with database components, allowing seamless display and editing of database records.

Setting the TeeGrid DataSource property to a TDataSet or TDataSource component will automatically create a TVirtualDBData object.

Usage

Automatic Creation

The simplest way to use TVirtualDBData is to assign a dataset or data source directly to the grid:

// Using TDataSet
TeeGrid1.DataSource := FDMemTable1;

// Using TDataSource
TeeGrid1.DataSource := DataSource2;

Manual Creation

You can also manually create and configure a TVirtualDBData instance:

uses Tee.GridData.DB;

// From TDataSource
TeeGrid1.Data := TVirtualDBData.From(DataSource1);

// From TDataSet
TeeGrid1.Data := TVirtualDBData.From(MyDataSet1);

Types

TVirtualFetchMode

Controls how records are fetched from the dataset:

• Automatic - Automatically determines fetch strategy based on dataset characteristics
• All - Fetches all records at once
• Partial - Fetches records on-demand (virtual mode)

Properties

DataSet · TDataSet

Provides read-only access to the underlying TDataSet being displayed in the grid.

var
  RecordCount: Integer;
begin
  if Assigned(TVirtualDBData(TeeGrid1.Data).DataSet) then
    RecordCount := TVirtualDBData(TeeGrid1.Data).DataSet.RecordCount;
end;

FetchMode · TVirtualFetchMode · default: "Automatic"

Controls the record fetching strategy. Set to All for smaller datasets or Partial for large datasets to improve performance.

var
  DBData: TVirtualDBData;
begin
  DBData := TVirtualDBData.From(FDQuery1);
  DBData.FetchMode := TVirtualFetchMode.Partial; // Virtual mode for large datasets
  TeeGrid1.Data := DBData;
end;

OwnsData · Boolean

Determines whether the TVirtualDBData instance owns and will free the associated dataset. Set to True if you want the data adapter to manage the dataset’s lifetime.

var
  DBData: TVirtualDBData;
begin
  DBData := TVirtualDBData.From(MyDataSet);
  DBData.OwnsData := True; // TVirtualDBData will free MyDataSet
  TeeGrid1.Data := DBData;
end;

Methods

Class Methods

From · class function

Creates a TVirtualData instance from a TComponent (TDataSet or TDataSource).

Signature:

class function From(const ASource: TComponent): TVirtualData; override;

Parameters:

• ASource - A TDataSet or TDataSource component

Returns: A new TVirtualDBData instance configured for the given data source.

Example:

uses Tee.GridData.DB;

var
  GridData: TVirtualData;
begin
  GridData := TVirtualDBData.From(FDQuery1);
  TeeGrid1.Data := GridData;
end;

LinkTo · class procedure

Links a TeeGrid column to a specific TField from the dataset.

Signature:

class procedure LinkTo(const AColumn: TColumn; const AField: TField); static;

Parameters:

• AColumn - The TColumn to link
• AField - The TField to link to the column

Example:

var
  Col: TColumn;
begin
  Col := TeeGrid1.Columns.Add;
  TVirtualDBData.LinkTo(Col, MyDataSet.FieldByName('CustomerName'));
end;

Instance Methods

AddColumns · procedure

Automatically adds columns to the grid based on the dataset fields.

Signature:

procedure AddColumns(const AColumns: TColumns); override;

Parameters:

• AColumns - The columns collection to populate

Example:

var
  DBData: TVirtualDBData;
begin
  DBData := TVirtualDBData.From(FDQuery1);
  TeeGrid1.Data := DBData;
  DBData.AddColumns(TeeGrid1.Columns); // Manually add columns
end;

AsFloat · function

Retrieves the floating-point value of a cell.

Signature:

function AsFloat(const AColumn: TColumn; const ARow: Integer): TFloat; override;

Parameters:

• AColumn - The column to read from
• ARow - The row index

Returns: The cell value as a floating-point number.

AsString · function

Retrieves the string representation of a cell value.

Signature:

function AsString(const AColumn: TColumn; const ARow: Integer): String; override;

Parameters:

• AColumn - The column to read from
• ARow - The row index

Returns: The cell value as a string.

Count · function

Returns the total number of rows (records) in the dataset.

Signature:

function Count: Integer; override;

Returns: The number of records in the dataset.

DataType · function

Returns the RTTI type information for a column’s data type.

Signature:

function DataType(const AColumn: TColumn): PTypeInfo; override;

Parameters:

• AColumn - The column to query

Returns: Pointer to the type information for the column’s field type.

Load · procedure

Loads or reloads the grid columns from the dataset.

Signature:

procedure Load(const AColumns: TColumns); override;

Parameters:

• AColumns - The columns collection to load into

ReadOnly · function

Determines if a column is read-only based on the field properties.

Signature:

function ReadOnly(const AColumn: TColumn): Boolean; override;

Parameters:

• AColumn - The column to check

Returns: True if the column’s field is read-only, False otherwise.

SetValue · procedure

Sets a cell value, updating the underlying dataset field.

Signature:

procedure SetValue(const AColumn: TColumn; const ARow: Integer; const AText: String); override;

Parameters:

• AColumn - The column to update
• ARow - The row index
• AText - The new value as a string

Example:

var
  DBData: TVirtualDBData;
begin
  DBData := TVirtualDBData(TeeGrid1.Data);
  DBData.SetValue(TeeGrid1.Columns[0], 5, 'New Value');
end;

AutoWidth · function

Calculates the optimal column width based on the data and painter.

Signature:

function AutoWidth(const APainter: TPainter; const AColumn: TColumn): Single; override;

Parameters:

• APainter - The painter used for measuring text
• AColumn - The column to measure

Returns: The calculated optimal width in pixels.

EditMode · procedure

Called when the grid enters or exits edit mode.

Signature:

procedure EditMode(const AMode: TEditMode); override;

Parameters:

• AMode - The edit mode state

Refresh · procedure

Refreshes the grid data from the dataset.

Signature:

procedure Refresh; override;

Example:

var
  DBData: TVirtualDBData;
begin
  DBData := TVirtualDBData(TeeGrid1.Data);
  DBData.Refresh; // Reload data from dataset
end;

Complete Examples

Basic Database Grid

uses
  VCLTee.Grid, Tee.GridData.DB, FireDAC.Comp.Client;

procedure TForm1.FormCreate(Sender: TObject);
begin
  // Automatic - just assign the dataset
  TeeGrid1.DataSource := FDQuery1;
end;

Advanced Configuration

uses
  VCLTee.Grid, Tee.GridData.DB, FireDAC.Comp.Client;

procedure TForm1.SetupGrid;
var
  DBData: TVirtualDBData;
begin
  // Create data adapter
  DBData := TVirtualDBData.From(FDQuery1);
  
  // Configure for large dataset
  DBData.FetchMode := TVirtualFetchMode.Partial;
  
  // Assign to grid
  TeeGrid1.Data := DBData;
  
  // Customize appearance
  TeeGrid1.Columns[0].Width := 200;
  TeeGrid1.Columns[1].Visible := False;
end;

Master-Detail Grids

uses
  VCLTee.Grid, Tee.GridData.DB;

procedure TForm1.SetupMasterDetail;
begin
  // Master grid
  MasterGrid.DataSource := MasterDataSet;
  
  // Detail grid
  DetailGrid.DataSource := DetailDataSet;
  
  // Link via dataset relationship
  DetailDataSet.MasterSource := MasterDataSource;
  DetailDataSet.MasterFields := 'CustomerID';
end;

Custom Field Linking

uses
  VCLTee.Grid, Tee.GridData.DB, Tee.Grid.Columns;

procedure TForm1.CreateCustomColumns;
var
  DBData: TVirtualDBData;
  Col: TColumn;
begin
  DBData := TVirtualDBData.From(MyDataSet);
  TeeGrid1.Data := DBData;
  
  // Manually create and link columns
  TeeGrid1.Columns.Clear;
  
  Col := TeeGrid1.Columns.Add;
  Col.Text := 'Customer';
  TVirtualDBData.LinkTo(Col, MyDataSet.FieldByName('CustomerName'));
  
  Col := TeeGrid1.Columns.Add;
  Col.Text := 'Total';
  TVirtualDBData.LinkTo(Col, MyDataSet.FieldByName('OrderTotal'));
end;

See Also

• TVirtualData - Base class for all data adapters
• TDataSet Binding - Guide to working with datasets
• Database Grid Examples - Complete examples