TDataset(from DataModule) event from main form unsuccess (SQLite)
lazarus / 16-Databases

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totya · 2018-03-06 20:26

Hi!

1. Create new application
2. Create new DataModule
3. Drop one Sqlite3Dataset to DataModule
4. Drop one DataSource to DataModule
5. DataSource.dataset:= Sqlite3Dataset

6. Drop on DBGrid to form1
7. DBGrid.DataSource:=DataModule.DataSource

Now, I want to access the DataModule/Dataset/AfterOpen event from the
Form1, so:

8. Click on the DBGrid events Datasource Dataset AfterOpen event
9. Fill this event empty: //

After run, I get exception: Invalid value for property.

What's wrong?

Thank you.

Lazarus 1.6.4 (64 bit)

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taazz · 2018-03-06 20:57

I'm guessing the creation order. Form1 can not find and link with the
controls in datamodule if the datamodule is not created before the
form1 and datamodule can not find and link with the event in form1
during creation before the form1 is created. That is a paradox and can
not be resolved automatically you need assign the event manually after
creation.

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totya · 2018-03-06 21:14

Hi!

Thank you taazz!

IIRC under Delphi it's working in similar situation, but possible my
memory is wrong.

So, how can I assign manually this event after creation?

Thanks!

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taazz · 2018-03-06 21:27

you make sure that the datamodule is created before form1 and you
write a OnCreate event in form with the code below.
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.FormCreate(Sender :TObject);begin 
DataModule1.Sqlite3Dataset1.AfterOpen = @Sqlite3Dataset1AfterOpen;end;

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totya · 2018-03-06 21:36

Thank you!

Form creation order is changed as you suggest. But then this code:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
Unit1; {$mode objfpc}{$H+} interface uses  Classes, SysUtils,
FileUtil, Forms, Controls, Graphics, Dialogs, DBGrids, db; type   {
TForm1 }   TForm1 = class(TForm)    DBGrid1: TDBGrid;    procedure
FormCreate(Sender: TObject);  private    procedure
Sqlite3Dataset1AfterOpen(DataSet: TDataSet);  end; var  Form1:
TForm1; implementation uses Unit2; {$R *.lfm} { TForm1 } procedure
TForm1.FormCreate(Sender: TObject);begin 
DataModule1.Sqlite3Dataset1.AfterOpen =
@Sqlite3Dataset1AfterOpen;end; procedure
TForm1.Sqlite3Dataset1AfterOpen(DataSet: TDataSet);begin end;  end. 
...cause compiler error: illegal expression

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taazz · 2018-03-07 05:46

Quote from: totya on March 06, 2018, 10:36:29 pm...cause compiler
error: illegal expression
No problems here find attached your example corrected, it compiles
properly.

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totya · 2018-03-07 17:13

Thanks, compile OK, but I got exception when project started.

Edit: But yes, I see my one error ":=" needed OMG. But your sample
halted for me when I run it, see attached picture.

Lazarus 1.6.4 x64

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taazz · 2018-03-08 04:52

Quote from: totya on March 07, 2018, 06:13:04 pmThanks, compile OK,
but I got exception when project started.

Edit: But yes, I see my one error ":=" needed OMG. But your sample
halted for me when I run it, see attached picture.

Lazarus 1.6.4 x64
clear the after post event in the datamodule.

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totya · 2018-03-08 17:46

Thank you taazz!