How to read block attributes?

1. Add DXF, DXFConv, and sgConsts to the uses section. Create a new procedure to read block attributes.

uses DXF, DXFConv, sgConsts;
...
procedure TForm1.ReadBlockAttributesClick(ASender: TObject);

2. Declare the local variable vDrawing and specify TsgDXFImage as its type.

More information about formats and their corresponding classes

Class	File format
TsgHPGLImage	PLT, HGL, HG, HPG, PLO, HP, HP1, HP2, HP3, HPGL, HPGL2, HPP, GL, GL2, PRN, SPL, RTL, PCL
TsgSVGImage	SVG, SVGZ
TsgDXFImage	DXF
TsgCADDXFImage	DXF
TsgDWFImage	DWF
TsgDWGImage	DWG
TsgCGMImage	CGM

Also, declare the insert. It is a block reference. Several inserts can reference the same block. Declare vInsert and specify TsgDXFInsert as its type.

var
  vDrawing: TsgDXFImage;
  vInsert: TsgDXFInsert;
  I, J: Integer;
  sContent: string;

3. Create an instance of the TsgDXFImage object, and then call the LoadFromFile method of this class. Remember to use the try...finally construct to avoid memory leaks.

begin
  vDrawing := TsgCADDXFImage.Create;
  try
    vDrawing.LoadFromFile('Entities.dxf');

4. Create a cycle to search entities in the current layout of vDrawing.

for I := 0 to vDrawing.CurrentLayout.Count - 1 do
    begin
      if vDrawing.CurrentLayout.Entities[I].EntType = ceInsert then
      begin
        vInsert := TsgDXFInsert(vDrawing.CurrentLayout.Entities[I]);
        for  J := 0 to vInsert.Attribs.Count - 1 do
         sContent := sContent + TsgDXFAttrib(vInsert.Attribs[J]).Tag + ' = ' +
            TsgDXFAttrib(vInsert.Attribs[J]).Value + #13;
        ShowMessage('Block name: ' + #13 + vInsert.Block.Name + #13 + sContent);
      end;
      sContent := '';
    end;
  finally
    vDrawing.Free;
  end;
end;

You have created the procedure to read block attributes.

The full code listing.

uses DXF, DXFConv, sgConsts;
...

implementation

procedure TForm1.ReadBlockAttributesClick(ASender: TObject);
var
  vDrawing: TsgCADDXFImage;
  vInsert: TsgDXFInsert;
  I, J: Integer;
  sContent: string;
begin
  vDrawing := TsgCADDXFImage.Create;
  try
    vDrawing.LoadFromFile('Entities.dxf');
    for I := 0 to vDrawing.CurrentLayout.Count - 1 do
    begin
      if vDrawing.CurrentLayout.Entities[I].EntType = ceInsert then
      begin
        vInsert := TsgDXFInsert(vDrawing.CurrentLayout.Entities[I]);
        for  J := 0 to vInsert.Attribs.Count - 1 do
         sContent := sContent + TsgDXFAttrib(vInsert.Attribs[J]).Tag + ' = ' +
            TsgDXFAttrib(vInsert.Attribs[J]).Value + #13;
        ShowMessage('Block name: ' + #13 + vInsert.Block.Name + #13 + sContent);
      end;
      sContent := '';
    end;
  finally
    vDrawing.Free;
  end;
end;