[New Programmer] Some questions
lazarus / 9-Editor

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fiqs · 2011-03-23 19:11

*SOLVED* 1. How do I delete a certain line from a .txt file?

2. How do I update the displayed text of a Memo? Like, I have one Memo
that displays the text from a .txt file, them I edit the file and add
in the end one new line, but the Memo doesn't show that new line. I'd
like to make one "Update" button.

*SOLVED* 3. I want to make a program with 3 different forms(e.g. A
calculator with 3 tabs, one for add, the other for substract and the
last one for multiply, just a example), how can I change from 1 form
to the other one? I've tried making 3 radio buttons, each one for a
tab, but I had some problems(I could change from the first to the
second/third, but couldn't change from the second to the first/third
or from the third to the first/second, used the "Form.Show" and the
"Form.Hide" commands). Why I couldn't change the tabs? Because, when I
tried to add the "Form.Show"/"Form.Hide" commands in the second or in
the third tabs, I get the following error:
Code: [Select]unit2.pas(38,20) Error: Identifier not found "TfrmAdic"
unit2.pas(40,1) Fatal: There were 2 errors compiling module, stopping

TfrmAdic is one of the forms, and I've already tried to add "frmAdic:
TfrmAdic;" in var, but when I do this, I get this error:

Code: [Select]unit2.pas(38,20) Error: Identifier not found "TfrmAdic"
unit2.pas(38,20) Error: Error in type definition
unit2.pas(40,1) Fatal: There were 2 errors compiling module, stopping
*SOLVED* 4. How do I work with Combo boxes? Like, I have one combo box
with every month, but how can I know what is the month that the person
choose?

*SOLVED* 5. How can I add both the ScrollBars in one Memo? I've
already tried "ssAutoBoth" and "ssBoth".

*SOLVED* 6. Can I learn Pascal/Lazarus with Delphi-based
tutorials/guides/etc.? Is there any differences?

I'm new with programming and Lazarus, as you can see. Thanks, and what
a great community Lazarus has

Edit.: Thanks typo and TurboRascal for the great help

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typo · 2011-03-23 19:17

What OS and Lazarus version are you using?

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fiqs · 2011-03-23 19:19

Oh, sorry. I'm using Windows XP SP3 with Lazarus IDE v0.9.28.2 beta.

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typo · 2011-03-23 19:34

4. How do I work with Combo boxes? Like, I have one combo box with
every month, but how can I know what is the month that the person
choose?

     The chosen item should appear as value of the property Text.

5. How can I add both the ScrollBars in one Memo? I've already tried
"ssAutoBoth" and "ssBoth".

     Any of these should do the job.

6. Can I learn Pascal/Lazarus with Delphi-based tutorials/guides/etc.?
Is there any differences?

     Yes, you can learn so.

1. How do I delete a certain line from a .txt file?

     You could load it on a TStringList, delete a specified line and
then save it.

2. How do I update the displayed text of a Memo? Like, I have one Memo
that displays the text from a .txt file, them I edit the file and add
in the end one new line, but the Memo doesn't show that new line. I'd
like to make one "Update" button.

     You simply need to reload the file on the TMemo.

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fiqs · 2011-03-23 19:41

Quote from: typo on March 23, 2011, 08:34:18 pm5. How can I add both
the ScrollBars in one Memo? I've already tried "ssAutoBoth" and
"ssBoth".

     Any of these should do the job.

Yeah, these should do the job, but it doesn't. Don't know why, but it
just show the text left in the following line.

Also, I noticed the "LazarusBrasil.Org" in your signature, and I'm
also a brazilian. If you want you can talk with me in portuguese,
don't know if it is against the rules of this forum.

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typo · 2011-03-23 19:48

Quotebut it doesn't. Don't know why, but it just show the text left in
the following line.
Set Wordwrap property to false.

Whenever possible, use English.

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fiqs · 2011-03-23 19:55

Quote from: typo on March 23, 2011, 08:48:28 pmQuotebut it doesn't.
Don't know why, but it just show the text left in the following line.
Set Wordwrap property to false.

Whenever possible, use English.

Oh yeah, it worked, thanks

And Ok, I think I can speak with English.

Any suggestion about the other questions?

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typo · 2011-03-23 20:06

Please have a look at the previous post again, I have edited it.

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TurboRascal · 2011-03-23 20:28

3. Show some code and someone will tell you what you did wrong. At
least paste the code which is source of your listed errors, that is
class declaration of your form and the code block where you call Show
method on your form.

6. Yes you can, and there are differences, but it can help you
nonetheless. I found Delphi books quite helpful.

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fiqs · 2011-03-23 21:47

Quote from: typo on March 23, 2011, 08:34:18 pm1. How do I delete a
certain line from a .txt file?

     You could load it on a TStringList, delete a specified line and
then save it.

2. How do I update the displayed text of a Memo? Like, I have one Memo
that displays the text from a .txt file, them I edit the file and add
in the end one new line, but the Memo doesn't show that new line. I'd
like to make one "Update" button.

     You simply need to reload the file on the TMemo.

1. Sorry but I didn't get the point, can you give me an example,
please?

2. You mean like this?
Code: [Select]Memo1.Lines.LoadFromFile('C:\textfile.txt')I've already
tried that, but it didn't work.


@TurboRascal
3. Ok, let's go.
Code: [Select]unit Unit2;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics,
Dialogs,
  StdCtrls, Unit3, Buttons, ExtCtrls, ColorBox, ComCtrls, ButtonPanel,
ExtDlgs,
  Menus, Process;

type

  { TfrmComp }

  TfrmComp = class(TForm)
    BtnAdicionar: TButton;
    BtnSair: TButton;
    GroupBox1: TGroupBox;
    Label1: TLabel;
    lblCopyright: TLabel;
    Memo1: TMemo;
    rBtnAdic: TRadioButton;
    rBtnComp: TRadioButton;
    rBtnInfo: TRadioButton;
    procedure BtnAdicionarClick(Sender: TObject);
    procedure BtnSairClick(Sender: TObject);
    procedure rBtnAdicChange(Sender: TObject);
    procedure rBtnInfoChange(Sender: TObject);
  private
    { private declarations }
  public
    { public declarations }
  end;

var
  frmComp: TfrmComp;
  //frmAdic: TfrmAdic;

implementation

{ TfrmComp }

procedure TfrmComp.BtnAdicionarClick(Sender: TObject);
begin
  Memo1.Lines.LoadFromFile('C:\comp.txt')
end;

procedure TfrmComp.BtnSairClick(Sender: TObject);
begin
  Application.Terminate;
end;

procedure TfrmComp.rBtnAdicChange(Sender: TObject);
begin
 // frmComp.Hide;
 // frmAdic.Show;
end;

procedure TfrmComp.rBtnInfoChange(Sender: TObject);
begin
end;

initialization
  {$I unit2.lrs}

end.I'm trying to do one kind of "appointment book"(or an agenda) for
students.
This is the second form, the first is working fine(I can change from
the first to second and from the first to the third), but the problem
is with the second and the third.

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typo · 2011-03-23 22:22

Code: [Select]var
   sl :TStringList;
 begin
   sl := TStringList.Create;
   try
     sl.LoadFromFile('C:\textfile.txt');
     sl.Delete(0);
     sl.SaveToFile('C:\textfile.txt');
   finally
     sl.Free;
   end;
 end;

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fiqs · 2011-03-23 22:44

Quote from: typo on March 23, 2011, 11:22:16 pmCode: [Select]var
   sl :TStringList;
 begin
   sl := TStringList.Create;
   try
     sl.LoadFromFile('C:\textfile.txt');
     sl.Delete(0);
     sl.SaveToFile('C:\textfile.txt');
   finally
     sl.Free;
   end;
 end;       

Oh, now I got it, thanks!
But, would you mind explain me what does this sl.Free means? I've
already seen it in other codes, but still not understanding.

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TurboRascal · 2011-03-23 23:08

Where did you define TfrmAdic class? In another unit? If so, why did
you declare frmAdic in this unit? If that's the problem you should add
the unit where frmAdic is declared to the uses statement in the
interface section of this unit, if not already done (is it possibly
"unit3" there?)... If so, simply removing the frmAdic var declaration
should do.

When that's sorted out correctly, it should compile ok, and your
rBtnAdicChange method should work fine...

And another thing, perhaps you could use Halt instead of
Application.Terminate. I think the latter makes abnormal program
termination...

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fiqs · 2011-03-23 23:23

Quote from: TurboRascal on March 24, 2011, 12:08:51 amWhere did you
define TfrmAdic class? In another unit? If so, why did you declare
frmAdic in this unit? If that's the problem you should add the unit
where frmAdic is declared to the uses statement in the interface
section of this unit, if not already done (is it possibly "unit3"
there?)... If so, simply removing the frmAdic var declaration should
do.

When that's sorted out correctly, it should compile ok, and your
rBtnAdicChange method should work fine...

And another thing, perhaps you could use Halt instead of
Application.Terminate. I think the latter makes abnormal program
termination...
Firstly, thank you for your help.
The TfrmAdic is defined in the Unit1(TfrmAdic). Yes, in another unit.
The problem is, when I try to add the Unit1 in the uses statment, I
get the following error:
Code: [Select]unit2.pas(9,18) Fatal: Circular unit reference between
Unit2 and Unit1
And when I remove the frmAdic var declaration(from the Unit2, right?)
I get the following error:
Code: [Select]unit2.pas(57,9) Error: Identifier not found "frmAdic"
This without the Unit1 in the uses statment, because with the Unit1, I
get the first error.
If you want, I can post all the Units here.

And about the use of Halt, you mean Application.Halt, just Halt or
what?

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TurboRascal · 2011-03-24 00:27

Quote from: fiqs on March 24, 2011, 12:23:41 amThe TfrmAdic is defined
in the Unit1(TfrmAdic). Yes, in another unit. The problem is, when I
try to add the Unit1 in the uses statment, I get the following error:
Code: [Select]unit2.pas(9,18) Fatal: Circular unit reference between
Unit2 and Unit1
And when I remove the frmAdic var declaration(from the Unit2, right?)
I get the following error:
Code: [Select]unit2.pas(57,9) Error: Identifier not found "frmAdic"
This without the Unit1 in the uses statment, because with the Unit1, I
get the first error.
If you want, I can post all the Units here.

And about the use of Halt, you mean Application.Halt, just Halt or
what?

The "circular reference" is obviously a consequence of you using unit2
in unit1, so this happens when you also use unit1 in unit2. However,
you must use unit1 in unit2 or you cannot call frmAdic. You can avoid
the circular dependency problem if you use those units from
implementation instead of interface section. That works only if you
don't have declarations in the used unit that the other unit needs,
but I guess you don't. So, add "uses unit1;" under the implementation
keyword and see if it works ok.

BTW I think it's wise to always use own units within implementation
whenever you don't need their declarations. That way you avoid
circular reference problems in advance.

And I mean just "Halt", not "Application.Halt". It' s a procedure
specifically meant for this use, to be called like that. You may also
use Halt(number) if you want the program to return a value IIRC...

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typo · 2011-03-24 01:45

sl.Free frees the newly created sl.

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fiqs · 2011-03-24 16:49

Quote from: TurboRascal on March 24, 2011, 01:27:26 amQuote from: fiqs
on March 24, 2011, 12:23:41 amThe TfrmAdic is defined in the
Unit1(TfrmAdic). Yes, in another unit. The problem is, when I try to
add the Unit1 in the uses statment, I get the following error:
Code: [Select]unit2.pas(9,18) Fatal: Circular unit reference between
Unit2 and Unit1
And when I remove the frmAdic var declaration(from the Unit2, right?)
I get the following error:
Code: [Select]unit2.pas(57,9) Error: Identifier not found "frmAdic"
This without the Unit1 in the uses statment, because with the Unit1, I
get the first error.
If you want, I can post all the Units here.

And about the use of Halt, you mean Application.Halt, just Halt or
what?

The "circular reference" is obviously a consequence of you using unit2
in unit1, so this happens when you also use unit1 in unit2. However,
you must use unit1 in unit2 or you cannot call frmAdic. You can avoid
the circular dependency problem if you use those units from
implementation instead of interface section. That works only if you
don't have declarations in the used unit that the other unit needs,
but I guess you don't. So, add "uses unit1;" under the implementation
keyword and see if it works ok.

BTW I think it's wise to always use own units within implementation
whenever you don't need their declarations. That way you avoid
circular reference problems in advance.

And I mean just "Halt", not "Application.Halt". It' s a procedure
specifically meant for this use, to be called like that. You may also
use Halt(number) if you want the program to return a value IIRC...

Finally, it worked! Thank you.

Another question, what do you think about this radiobutton method
using Form.Show? Do you know any better methods?

And again, thanks!

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typo · 2011-03-24 17:01

QuoteAnother question, what do you think about this radiobutton method
using Form.Show? Do you know any better methods?
I didn't quite understand how you did it. You may need to BringToFront
the form that you showed up last.

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TurboRascal · 2011-03-24 19:01

I think that way you used to hide and show forms should be right, if
it works ok for you...