[Solved] How to modify OnGetText method in TDBf
lazarus / 16-Databases

----------------------------------------------------------------------
xaver13 · 2012-09-16 18:17

need to use OnGetText method to convert 1251 code page DBF fields to
utf8
I was inspired here:
http://www.lazarus.freepascal.org/index.php?topic=11213.0
I tried the code:
Code: [Select]unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, db, dbf, FileUtil, Forms, Controls, Graphics,
Dialogs,
  DBGrids, DbCtrls, StdCtrls;

type

  { TForm1 }

  TForm1 = class(TForm)
    Datasource1: TDatasource;
    Dbf1: TDbf;
    DBGrid1: TDBGrid;
    DBNavigator1: TDBNavigator;
    Label1: TLabel;
    procedure Dbf1AfterOpen(DataSet: TDataSet);
    procedure DBGrid1GetCellHint(Sender: TObject; Column: TColumn;
      var AText: String);
  private
    { private declarations }
  public
    { public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{ TForm1 }

//type
//Tmethod = procedure() of object;

Procedure Konv(Sender:Tfield; var aText:String; DisplayText: Boolean =
true);
begin
  //aText:=Trim(Sender.AsString);
  aText:=Utf8ToAnsi(Sender.AsString);
end;


procedure TForm1.Dbf1AfterOpen(DataSet: TDataSet);
  var i:integer;
      aText: String;
  // var m:Tmethod;
  begin
  For i:=0 to Dbf1.FieldCount-1 do
      If Dbf1.Fields[i].DataType=ftString then
      //label1.caption:=label1.caption+'s';
      Dbf1.Fields[i].OnGetText:=@Konv;
  end;
end.  
But I am getting an error
Code: [Select]unit1.pas(57,33) Error: Incompatible types: got
"<address of procedure(TField,var
AnsiString,Boolean="TRUE");Register>" expected "<procedure variable
type of procedure(TField,var AnsiString,Boolean) of object;Register>"
on Code: [Select]Dbf1.Fields[i].OnGetText:=@Konv;
 line.
Thank You very much for  help.
Regards,

----------------------------------------------------------------------
marcov · 2012-09-16 19:12

The main problem is that you declared a procedure, not a method.

A potentially secondary problem might be the default parameter ( 
DisplayText: Boolean = true), I don't know if the compiler accepts
that.

----------------------------------------------------------------------
xaver13 · 2012-09-16 19:27

Thank you very much.
As I wrote in first post I was inspired here
http://www.lazarus.freepascal.org/index.php?topic=11213.0
in this forum. O.K. this is wrong.

Now I tried:
Code: [Select]Function Konv(Sender:Tfield; var aText:String;
DisplayText: Boolean = true):string;
begin
  Konv:=Utf8ToAnsi(Sender.AsString);
end;  

but the Error onCode: [Select]Dbf1.Fields[i].OnGetText:=@Konv;
Incompatible types: got "<address of function(TField,var
AnsiString,Boolean="TRUE"):AnsiString;Register>" expected "<procedure
variable type of procedure(TField,var AnsiString,Boolean) of
object;Register>"

remains the same  .

Coud you please tell me how to declare and use such method correctly
or where to find correct answer?

----------------------------------------------------------------------
taazz · 2012-09-16 20:46

Two problems I see in your code.

1) Konv is declared as a function while the OngetText events expects a
procedure.
2) It is not a method of an object.

Using your code from your first post here are the modifications.

Code: [Select]unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, db, dbf, FileUtil, Forms, Controls, Graphics,
Dialogs,
  DBGrids, DbCtrls, StdCtrls;

type

  { TForm1 }

  TForm1 = class(TForm)
    Datasource1: TDatasource;
    Dbf1: TDbf;
    DBGrid1: TDBGrid;
    DBNavigator1: TDBNavigator;
    Label1: TLabel;
    procedure Dbf1AfterOpen(DataSet: TDataSet);
    procedure DBGrid1GetCellHint(Sender: TObject; Column: TColumn;
      var AText: String);
  private
    { private declarations }
  public
    { public declarations }
    Procedure Convert(Sender:Tfield; var aText:String; DisplayText:
Boolean);
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{ TForm1 }

//type
//Tmethod = procedure() of object;

Procedure Konv(Sender:Tfield; var aText:String; DisplayText: Boolean =
true);
begin
  //aText:=Trim(Sender.AsString);
  aText:=Utf8ToAnsi(Sender.AsString);
end;


procedure TForm1.Dbf1AfterOpen(DataSet: TDataSet);
  var i:integer;
      aText: String;
  // var m:Tmethod;
  begin
  For i:=0 to Dbf1.FieldCount-1 do
      If Dbf1.Fields[i].DataType=ftString then
      //label1.caption:=label1.caption+'s';
      Dbf1.Fields[i].OnGetText:=@Convert;
  end;
end.  

Procedure TForm1.Convert(Sender:Tfield; var aText:String; DisplayText:
Boolean);
begin
  if DisplayText then
    aText:=Utf8ToAnsi(Sender.AsString)
  else
    aText := Sender.AsString;
end;

----------------------------------------------------------------------
xaver13 · 2012-09-17 07:37

Thank you, taazz!

Working code bellow. I had to move declarations of methods from public
section some lines up - to Tform class, why?

Code: [Select]unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, db, dbf, FileUtil, Forms, Controls, Graphics,
Dialogs,
  DBGrids, DbCtrls, StdCtrls;

type

  { TForm1 }

  TForm1 = class(TForm)
    Datasource1: TDatasource;
    Dbf1: TDbf;
    DBGrid1: TDBGrid;
    DBNavigator1: TDBNavigator;
    Label1: TLabel;
    procedure Dbf1AfterOpen(DataSet: TDataSet);
    Procedure Convert(Sender:Tfield; var aText:String; DisplayText:
Boolean);

  Private
    { private declarations }
  Public
    { public declarations }
//    Procedure Convert(Sender:Tfield; var aText:String; DisplayText:
Boolean);
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{ TForm1 }

Procedure TForm1.Convert(Sender:Tfield; var aText:String; DisplayText:
Boolean=True);
begin
  if DisplayText then
    aText:=AnsiToUtf8(Sender.AsString)
    else
    aText:=AnsiToUtf8(Sender.AsString)
 end;



procedure TForm1.Dbf1AfterOpen(DataSet: TDataSet);
  var i:integer;
      aText: String;
  begin
    For i:=0 to Dbf1.FieldCount-1 do
      If Dbf1.Fields[i].DataType=ftString then
        Dbf1.Fields[i].OnGetText:=@Convert;
  end;


end.
           
[code]