TGridDataStrings

String-based grid data classes for TStringGrid emulation and virtual mode

Overview

The Tee.GridData.Strings unit provides two classes for working with string-based grid data:

1. TVirtualModeData - A virtual data class for custom “Column x Row” grids using events
2. TStringsData - A TStringGrid emulator that maintains an internal array of strings

These classes are perfect for creating simple grids without database binding, similar to the traditional TStringGrid component.

TVirtualModeData

A lightweight virtual data class that uses events to provide cell values on-demand.

Constructor

Create · constructor

Creates a new virtual mode data instance.

Signature:

Constructor Create(const AColumns: Integer = 0; 
                   const ARows: Integer = 0; 
                   const DefaultWidth: Single = 0); virtual;

Parameters:

• AColumns - Initial number of columns (default: 0)
• ARows - Initial number of rows (default: 0)
• DefaultWidth - Optional default column width for faster rendering (default: 0)

Example:

var
  Data: TVirtualModeData;
begin
  // Create grid with 10 columns, 1000 rows, 60px column width
  Data := TVirtualModeData.Create(10, 1000, 60);
  TeeGrid1.Data := Data;
end;

Properties

Columns · Integer · default: "0"

Gets or sets the number of columns in the grid.

Example:

var
  Data: TVirtualModeData;
begin
  Data := TVirtualModeData.Create;
  Data.Columns := 5;
  Data.Rows := 10;
  TeeGrid1.Data := Data;
end;

Rows · Integer · default: "0"

Gets or sets the number of rows in the grid.

Example:

Data.Rows := 100; // Set to 100 rows

Headers · String

Gets or sets the header text for a specific column.

Signature:

property Headers[const Column: Integer]: String read GetHeader write SetHeader;

Parameters:

• Column - Zero-based column index

Example:

Data.Headers[0] := 'Name';
Data.Headers[1] := 'Company';
Data.Headers[2] := 'Email';

ColumnList · TColumns

Provides read-only access to the internal columns collection.

Example:

var
  Col: TColumn;
begin
  Col := Data.ColumnList[0];
  ShowMessage(Col.Text);
end;

Events

OnGetValue · TOnVirtualData

Event fired when the grid needs to retrieve a cell value.

Signature:

TOnVirtualData = procedure(Sender: TObject;
                           const AColumn: TColumn;
                           const ARow: Integer;
                           var AValue: String) of object;

Parameters:

• Sender - The data object
• AColumn - The column being queried
• ARow - The row index
• AValue - Output parameter - set this to the cell value

Example:

procedure TForm1.GetCellValue(Sender: TObject; const AColumn: TColumn; 
  const ARow: Integer; var AValue: String);
begin
  AValue := Format('Cell[%d,%d]', [Data.IndexOf(AColumn), ARow]);
end;

// Setup:
Data.OnGetValue := GetCellValue;

OnSetValue · TOnVirtualData

Event fired when the grid needs to update a cell value.

Signature:

TOnVirtualData = procedure(Sender: TObject;
                           const AColumn: TColumn;
                           const ARow: Integer;
                           var AValue: String) of object;

Parameters:

• Sender - The data object
• AColumn - The column being updated
• ARow - The row index
• AValue - The new cell value

Example:

procedure TForm1.SetCellValue(Sender: TObject; const AColumn: TColumn; 
  const ARow: Integer; var AValue: String);
begin
  // Store value in your data structure
  MyDataArray[ARow, Data.IndexOf(AColumn)] := AValue;
end;

// Setup:
Data.OnSetValue := SetCellValue;

Methods

Resize · procedure

Resizes the grid to the specified dimensions.

Signature:

procedure Resize(const AColumns, ARows: Integer);

Parameters:

• AColumns - New number of columns
• ARows - New number of rows

Example:

Data.Resize(10, 20); // Resize to 10 columns x 20 rows

IndexOf · function

Returns the zero-based index of a column.

Signature:

function IndexOf(const AColumn: TColumn): Integer; inline;

Parameters:

• AColumn - The column to find

Returns: The column’s index, or -1 if not found.

Complete Example

uses
  VCLTee.Grid, Tee.GridData.Strings;

type
  TForm1 = class(TForm)
    TeeGrid1: TTeeGrid;
    procedure FormCreate(Sender: TObject);
  private
    Data: TVirtualModeData;
    procedure GetCell(Sender: TObject; const AColumn: TColumn; 
      const ARow: Integer; var AValue: String);
    procedure SetCell(Sender: TObject; const AColumn: TColumn; 
      const ARow: Integer; var AValue: String);
  end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  // Create data with 10 columns, 1000 rows, 60px width
  Data := TVirtualModeData.Create(10, 1000, 60);
  
  // Set headers
  Data.Headers[0] := 'ID';
  Data.Headers[1] := 'Name';
  Data.Headers[2] := 'Email';
  
  // Hook up events
  Data.OnGetValue := GetCell;
  Data.OnSetValue := SetCell;
  
  // Assign to grid
  TeeGrid1.Data := Data;
end;

procedure TForm1.GetCell(Sender: TObject; const AColumn: TColumn; 
  const ARow: Integer; var AValue: String);
var
  ColIndex: Integer;
begin
  ColIndex := Data.IndexOf(AColumn);
  
  // Generate cell value
  case ColIndex of
    0: AValue := IntToStr(ARow + 1);  // ID
    1: AValue := 'User ' + IntToStr(ARow + 1);  // Name
    2: AValue := Format('[e-mail]', [ARow + 1]);  // Email
  else
    AValue := Format('Data[%d,%d]', [ColIndex, ARow]);
  end;
end;

procedure TForm1.SetCell(Sender: TObject; const AColumn: TColumn; 
  const ARow: Integer; var AValue: String);
begin
  // Handle cell editing
  ShowMessage(Format('Cell [%d,%d] set to: %s', 
    [Data.IndexOf(AColumn), ARow, AValue]));
end;

TStringsData

Derived from TVirtualModeData, this class maintains an internal array of strings for each cell, similar to TStringGrid.

Constructor

Create · constructor

Creates a new strings data instance.

Signature:

Constructor Create(const AColumns: Integer = 0; const ARows: Integer = 0); 

Parameters:

• AColumns - Initial number of columns (default: 0)
• ARows - Initial number of rows (default: 0)

Example:

var
  Data: TStringsData;
begin
  // Create with optional size
  Data := TStringsData.Create(5, 4);
  TeeGrid1.Data := Data;
end;

Properties

Cells · String · default: true

Gets or sets the value of a specific cell. This is the default array property.

Signature:

property Cells[const Column, Row: Integer]: String read GetCell write SetCell; default;

Parameters:

• Column - Zero-based column index
• Row - Zero-based row index

Example:

var
  Data: TStringsData;
begin
  Data := TStringsData.Create;
  Data.Columns := 3;
  Data.Rows := 2;
  
  // Set cell values using default property
  Data[0, 0] := 'Name';
  Data[1, 0] := 'Age';
  Data[2, 0] := 'Email';
  
  Data[0, 1] := 'John';
  Data[1, 1] := '30';
  Data[2, 1] := '[e-mail]';
  
  // Read values
  ShowMessage(Data[0, 1]); // Shows 'John'
end;

All properties from TVirtualModeData are also available (Columns, Rows, Headers, etc.).

Complete Example

uses
  VCLTee.Grid, Tee.GridData.Strings;

type
  TForm1 = class(TForm)
    TeeGrid1: TTeeGrid;
    procedure FormCreate(Sender: TObject);
  end;

procedure TForm1.FormCreate(Sender: TObject);
var
  Data: TStringsData;
  i: Integer;
begin
  // Create data
  Data := TStringsData.Create;
  
  // Set size
  Data.Columns := 5;
  Data.Rows := 10;
  
  // Set headers
  Data.Headers[0] := 'ID';
  Data.Headers[1] := 'Company';
  Data.Headers[2] := 'Contact';
  Data.Headers[3] := 'Phone';
  Data.Headers[4] := 'Email';
  
  // Fill data
  for i := 0 to 9 do
  begin
    Data[0, i] := IntToStr(i + 1);
    Data[1, i] := 'Company ' + IntToStr(i + 1);
    Data[2, i] := 'Contact ' + IntToStr(i + 1);
    Data[3, i] := '555-' + Format('%.4d', [1000 + i]);
    Data[4, i] := Format('contact%d@company%d.com', [i + 1, i + 1]);
  end;
  
  // Assign to grid
  TeeGrid1.Data := Data;
end;

Dynamic Data Modification

uses
  VCLTee.Grid, Tee.GridData.Strings;

procedure TForm1.AddRow(const Name, Email: String);
var
  Data: TStringsData;
  NewRow: Integer;
begin
  Data := TStringsData(TeeGrid1.Data);
  
  // Add a new row
  NewRow := Data.Rows;
  Data.Rows := Data.Rows + 1;
  
  // Set values
  Data[0, NewRow] := IntToStr(NewRow + 1);
  Data[1, NewRow] := Name;
  Data[2, NewRow] := Email;
  
  // Refresh grid
  TeeGrid1.Invalidate;
end;

procedure TForm1.DeleteRow(const ARow: Integer);
var
  Data: TStringsData;
  i, j: Integer;
begin
  Data := TStringsData(TeeGrid1.Data);
  
  // Shift rows up
  for i := ARow to Data.Rows - 2 do
    for j := 0 to Data.Columns - 1 do
      Data[j, i] := Data[j, i + 1];
  
  // Remove last row
  Data.Rows := Data.Rows - 1;
  
  TeeGrid1.Invalidate;
end;

Importing from CSV

uses
  VCLTee.Grid, Tee.GridData.Strings, System.Classes, System.SysUtils;

procedure TForm1.LoadFromCSV(const FileName: String);
var
  Data: TStringsData;
  Lines: TStringList;
  Row, Col: Integer;
  Values: TArray<String>;
begin
  Data := TStringsData.Create;
  Lines := TStringList.Create;
  try
    Lines.LoadFromFile(FileName);
    
    if Lines.Count = 0 then Exit;
    
    // First line = headers
    Values := Lines[0].Split([',']);
    Data.Columns := Length(Values);
    for Col := 0 to High(Values) do
      Data.Headers[Col] := Values[Col].Trim;
    
    // Remaining lines = data
    Data.Rows := Lines.Count - 1;
    for Row := 1 to Lines.Count - 1 do
    begin
      Values := Lines[Row].Split([',']);
      for Col := 0 to Min(High(Values), Data.Columns - 1) do
        Data[Col, Row - 1] := Values[Col].Trim;
    end;
    
    TeeGrid1.Data := Data;
  finally
    Lines.Free;
  end;
end;

Performance Comparison

TVirtualModeData

Pros:

• Minimal memory usage (no data stored internally)
• Perfect for very large datasets
• Data stays in your own data structures

Cons:

• Requires implementing event handlers
• You manage data storage

Best for: Large datasets (1M+ rows), computed values, data from external sources

TStringsData

Pros:

• Simple to use (like TStringGrid)
• No event handlers needed
• Easy data manipulation

Cons:

• Stores all data in memory
• Higher memory usage for large datasets

Best for: Small to medium datasets (up to 100K rows), simple grids, quick prototypes

See Also

• TVirtualData - Base virtual data class
• Strings Data Guide - Complete guide to string-based grids
• Custom Virtual Data - Creating custom data sources
• Basic Grid Example - Simple grid examples