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lazarus / 16-Databases

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allanregistos · 2014-05-20 05:39

Hi all,

I've been using Lazarus IDE now for the past months. My previous PL
was vb.net, and even I don't like it, I've used it because its easy
and fast to create apps. Now, I have created few utilities(LOBs)
database applications using Lazarus for the company where I presently
working.  I just want to make sure that my code is friendly to others,
that is, not like a huge spaghetti code.
(Disclaimer: My knowledge of Objects is pretty vague when applied to
Programming(OOP). So my programming method is mostly procedural.)

I did not use an database abstracting method to let my app work with
any databases(because I have no knowledge how to do this yet),  also
because I am a fan of PostgreSQL and since my code is in-house and not
to be released in the public domain. I am interested from anyone's
expertise if what I am doing with my code is at least acceptable. 
Also, I just want to make sure that I am separating the GUI from the
database layer.

Part of my work is the code snippet below. The code will let me delete
a record from the database. I have separated the db queries in a
separate unit(dbqueries). Most of my code resembles below.

My question is, can this code be accepted as doing the separation of
GUI from the database layer?

Thank you...

Code: [Select]     BoxStyle := MB_ICONQUESTION + MB_YESNO +
MB_DEFBUTTON2;
      FMT_Message := 'Do you really want to delete: ''%s'' from the
record?';
      FMT_Message := Format(FMT_Message,[ColorNametbDel]);
      Reply := Application.MessageBox(PChar(FMT_Message),
pChar(APPLICATION_Title), BoxStyle);
      if Reply = IDYES then begin
          if dbqueries.DeleteInkRecord('ink_inv',INK_INV_ID_EDIT) Then
begin
             if menuShowEmptyInk.Checked Then CheckEmptyInk:= true
else CheckEmptyInk:= false;
             dbqueries.FillColorGrid(InkDataGrid,SQLQuery1,SQLTransact
ion1,Datasource1,CheckEmptyInk);
             FMT_Message := 'Ink: ''%s'' has been deleted from the
inventory database.';
             FMT_Message := Format(FMT_Message,[ColorNametbDel]);
             mMessages.Append(FMT_Message);
             MessageDlg(APPLICATION_Title,
              FMT_Message, mtInformation,
              [mbOK], 0);
          end
          else
             MessageDlg(APPLICATION_Title,
              'Ink: ''' + ColorNametbDel + ''' cannot be deleted from
the database.', mtError,
              [mbOK], 0);
      end;

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kpeters58 · 2014-05-20 17:38

You have not given us enough to form an opinion since only 1 (maybe 2)
lines are really concerned with db access; maybe this will help you
form an opinion as where you should go:

http://www.codeproject.com/Articles/493389/Four-ways-of-passing-data-
between-layers

I also noted your desire to write "code <that> is friendly to others"
and I find that your code is more verbose than need be (that's just my
very personal opinion and not meant as negative criticism at all):

Code: [Select]      Reply :=
Application.MessageBox(PChar(FMT_Message), pChar(APPLICATION_Title),
BoxStyle);
      if Reply = IDYES then
I would shorten to

   Code: [Select]   if Application.MessageBox(PChar(FMT_Message),
pChar(APPLICATION_Title), BoxStyle) = IDYES then
Similarly:

Code: [Select]if menuShowEmptyInk.Checked Then CheckEmptyInk:= true
else CheckEmptyInk:= false;
Could be:

Code: [Select]CheckEmptyInk := menuShowEmptyInk.Checked;
It looks like you don't need CheckEmptyInk at all - you could just
replace it in your call to FillColorgrid with
'menuShowEmptyInk.Checked' (but then I don't have all the code and
could thus be wrong)


Less is *usually* more when it comes to readability and bug count.

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allanregistos · 2014-05-22 06:12

Quote from: kpeters58 on May 20, 2014, 07:38:19 pmYou have not given
us enough to form an opinion since only 1 (maybe 2) lines are really
concerned with db access; maybe this will help you form an opinion as
where you should go:

http://www.codeproject.com/Articles/493389/Four-ways-of-passing-data-
between-layers
Thanks for the link.  I stated that all of my code resembles with what
I provided. Sorry if that is not enough. Its all about DB access, the
queries including inserts/delete are separated in a unit.  My software
is all about inventory of existing raw materials such as paper rolls. 
I am not really good into OOP concepts.  However, I will try to
explore the TIOPF approach. Downloaded the Database Desktop but
unfortunately in Ubuntu 12.04/64-bit env., it cannot find the
postgresql client libraries even if I copied the libpq* in the same
dir where the 'Database Desktop' was located but that another story.
Quote from: kpeters58 on May 20, 2014, 07:38:19 pmI also noted your
desire to write "code <that> is friendly to others" and I find that
your code is more verbose than need be (that's just my very personal
opinion and not meant as negative criticism at all):

Code: [Select]      Reply :=
Application.MessageBox(PChar(FMT_Message), pChar(APPLICATION_Title),
BoxStyle);
      if Reply = IDYES then
I would shorten to

   Code: [Select]   if Application.MessageBox(PChar(FMT_Message),
pChar(APPLICATION_Title), BoxStyle) = IDYES then
Similarly:

Code: [Select]if menuShowEmptyInk.Checked Then CheckEmptyInk:= true
else CheckEmptyInk:= false;
Could be:

Code: [Select]CheckEmptyInk := menuShowEmptyInk.Checked;
It looks like you don't need CheckEmptyInk at all - you could just
replace it in your call to FillColorgrid with
'menuShowEmptyInk.Checked' (but then I don't have all the code and
could thus be wrong)

Less is *usually* more when it comes to readability and bug count.

That helps a lot, thanks kpeters58.
-Allan

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fpcoder · 2014-06-04 01:50

Might be a far shot regarding your libpq libraries, but under
Linux/Ubuntu it may be necessary to create a symbolic link, see link:

http://wiki.freepascal.org/postgres#Error:_.22Can_not_load_PostgreSQL_
client_library_.22libpq.dll.22.22