TVarBytesField Class

TVarBytesField represents a variable-length untyped binary field in a dataset.

Pascal

TVarBytesField = class(TBytesField);

C++

class TVarBytesField : public TBytesField;

File

Description

A variable bytes field value is a set of bytes of variable size, with the actual length of the value stored in the first two bytes.

If you use the Fields editor at design time to create a persistent field component for the variable bytes field, you can access it by name at runtime. When using dynamic field components, you can access the TVarBytesField instance using the dataset's Fields property or FieldByName method.

Delphi Examples:

Copy Code

{
This example requires a button, a test edit, and a populated
ClientDataSet.  Pipe the ClientDataSet through a DataSource
to a DGGrid or DBNavigator to control the current field.
Cast the data correctly according to the field type when
assigning to the test edit.
}

{$IFNDEF UNICODE}
uses SwSystem;
{$ENDIF}

procedure TForm1.Button1Click(Sender: TObject);
var MyBuffer: Pointer;
begin
{ Retrieve the "raw" data from Field1 }
with CDS.Fields[0] do
  begin
    if not IsBlob then { this does not work for BLOB fields }
    begin
      { Allocate space }
      MyBuffer:= GetMemory(DataSize);
      try
        if not GetData(MyBuffer) then
          MessageDlg(DisplayName + ' is NULL', mtInformation, [mbOK], 0)
        else
          { Do something with the data };
          Edit1.Text:= string(PAnsiChar(MyBuffer)); // for a stringfield
      finally
        { Free the space }
        FreeMem(MyBuffer, DataSize);
      end;
    end;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
{$IFDEF UNICODE}
  CDS.LoadFromFile(GetCurrentDir + '\CDS.XML');
{$ELSE}
  CDS.LoadFromFile(gsAppPath + 'CDS.XML');
{$ENDIF}
end;