DBase add new fields [SOLVED]
lazarus / 16-Databases

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timcs · 2013-02-07 18:10

Hi

I am trying to add a new field to a DBase database and all methods I
have tried either do not error but not add the field or error and fail
to add the new field

I am trying to add a new integer field with a length of 10.

This method errors:
Code: [Select]dbf1.Active:=false;

               dbf1.DbfFieldDefs.AddFieldDef.DisplayName:='idlink';
               dbf1.DbfFieldDefs.AddFieldDef.Size:=10;
               dbf1.DbfFieldDefs.AddFieldDef.FieldType:=ftInteger;
               dbf1.RestructureTable(dbf1.DbfFieldDefs,true);
               dbf1.open;
               dbf1.active := true      


this method does not error but does not add the field either

Code: [Select]With DBF1 do
    begin
    With FieldDefs do
      begin
      Add('idlink',ftInteger,10);
      end;

    Exclusive:=false;
    Open;
    active := true;

   end;

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timcs · 2013-02-09 15:36

I thought I was getting somewhere when I found this post :
http://www.lazarus.freepascal.org/index.php/topic,8567.msg42023.html

However when I compile the program using the TDbfFieldDefs I get :

Quotedbff.pas(20,30) Error: Identifier not found "TDbfFieldDefs"

So that stops the program from working

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BigChimp · 2013-02-09 15:56

OS, Lazarus version, small example project (project/publish project,
zip, attach to post) would probably help

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BigChimp · 2013-02-09 16:00

Quote from: timcs on February 07, 2013, 07:10:10 pmThis method errors:
Code: [Select]dbf1.Active:=false;

               dbf1.DbfFieldDefs.AddFieldDef.DisplayName:='idlink';
               dbf1.DbfFieldDefs.AddFieldDef.Size:=10;
               dbf1.DbfFieldDefs.AddFieldDef.FieldType:=ftInteger;
That code seems weird. How is the compiler supposed to know you're all
referring to the same field you're adding, not to say 3 different
fields?

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timcs · 2013-02-09 17:25

That code was really a stab in the dark any way

OS:Windows XP/Vista
Lazarus version : 10

Code from the DBF PDF I am trying to use is :

Code: [Select]NewFieldDefs: TDbfFieldDefs;
NewFieldDef: TDbfFieldDef;
Dbf1: TDbf;
...
// create new field list
NewFieldDefs := TDbfFieldDefs. Create ( Self);
// assign current list
NewFieldDefs. Assign ( Dbf1. DbfFieldDefs);
// assume first field is string , 20 wide , make larger to 40
NewFieldDefs. Items [0]. Size := 40;
// rename second field to 'RENAMED '
NewFieldDefs. Items [1]. FieldName := 'RENAMED ';
// add a float field
NewFieldDef := NewFieldDefs. AddFieldDef;
NewFieldDef. FieldName := 'NEW_FLOAT ';
NewFieldDef. FieldType := ftFloat;
NewFieldDef. Size := 10;
NewFieldDef. Precision := 3;
// restructure table and pack
Dbf1. Restructure( NewFieldDefs , true);
// restructure table and not pack
// Dbf1. Restructure( NewFieldDefs , false );
// free mem
NewFieldDefs. Free;

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howardpc · 2013-02-09 17:30

I don't think Restructure is method to use. The following snippet
compiles and creates an indexed table for me:
Code: [Select]...
uses dbf, dbf_fields;

{ TForm1 }

procedure TForm1.BCreateTblClick(Sender: TObject);
  var dbDefs: TDbfFieldDefs;
      dbTbl: TDbf;
  begin
    dbTbl:= TDbf.Create(nil);
    try
    dbTbl.OpenMode:= omAutoCreate;
    dbTbl.Exclusive:= True;
    dbTbl.TableName:= '\data\ExTbl.dbf';
    dbDefs := TDbfFieldDefs.Create(nil);
    try
      dbDefs.Add('IDLINK',ftInteger,10);
      dbDefs.Add('IDDESCR',ftString,15);
      dbTbl.CreateTableEx(dbDefs);
    finally
      dbDefs.Free;
    end;
    dbTbl.Open;
    dbTbl.AddIndex('DescrIdx', 'IDDESCR', [ixPrimary]);
    dbTbl.IndexName:='DescrIdx';
    dbTbl.Edit;
    dbTbl.AppendRecord([10,'ten']);
    dbTbl.AppendRecord([11,'eleven']);
    dbTbl.AppendRecord([12,'twelve']);
    // ... display records etc.
    finally
      dbTbl.Close;
      dbTbl.Free;
    end;
  end;

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timcs · 2013-02-09 18:02

Howard

Thanks for this I didn't know that dbf_fields was a separate unit to
include. I will try again to create the new field and come back . If
it has worked I will state this thread as SOLVED.