Raul wrote:

On 12/20/2014 10:24 AM, TD wrote:
> Uli, Walter thank you so much for helping!  I have searched the EWB manual and this forum for information on the OnCommit event and have found nothing.  Can you guys give me an example as to how to use / work with this event?

I don't believe there is a OnCommit event - i assume what they meant was
that you call "Commit" and then wait for either AfterCommit or
OnCommitError events.

I suggest you review the datasets section :

http://www.elevatesoft.com/manual?action=topics&id=ewb1§ion=using_datasets

It really does cover all the details on how this works. Start with
DataSet Architecture and at least read Transactions (though i'd suggest
you read them all). For example you need to be aware of the
TransactionLevel : only if it reaches 0 does the data get posted to back
end server, etc.

Raul

Any chance someone could post a code example of how to use AfterCommit to tell when the data has actually been written to the database?

TD

Yes I gave you the wrong event names:

if Database.InTransaction then
 begin
   Database.AfterCommit   := AfterCommit;
   Database.OnCommitError := OnCommitError;

   Database.Commit;
 end;


I attached a full example on Dec 1 in this thread ......

Walter

Walter Matte wrote:


Yes I gave you the wrong event names:

if Database.InTransaction then
 begin
   Database.AfterCommit   := AfterCommit;
   Database.OnCommitError := OnCommitError;

   Database.Commit;
 end;


I attached a full example on Dec 1 in this thread ......

Walter


Thank you Walter.  I will take a look again at your example.  
TD

On 12/20/2014 2:28 PM, TD wrote:
> Any chance someone could post a code example of how to use AfterCommit to tell when the data has actually been written to the database?

TD,

AfterCommit simply means that the database operation has completed on
the server - that's all there is to it.

Due to the asynchronous nature of javascript this the only way of
letting you know of this - due to the network connection etc this could
be seconds in the future.

How your app reacts is unique to each application - for example if you
have a Save button that commits the transaction then upon receiving
AfterCommit you can disable or hide the button; or maybe you had a
window up telling user to wait so now you can hide the window and move on.

The longer explanation goes like this:

- TDataSet DOES NOT directly represent dbisam/edb or any other back end
database you are using.

- TDataset represents a "local" copy of data that was downloaded from
server in JSON format and loaded into TDataset.

- Any editing/inserts/deletes only modify the local data and not the
actual back-end database.

- If you do wish to modify the actual back-end database you must use
transactions. Specifically once you call StartTransaction all the
changes you make to tdataset will be logged (note again that this is all
logged locally at this point still).

- when you call Commit the TDataBase takes all these changes, and starts
a new TServerRequest (basically a web POST request to the back-end web
server) and waits for the RequestComplete event.

- Assuming your connection to the server works at some point in the
future RequestComplete is fired which in turn causes the TDataBase to
call AfterCommit event.

Raul

Uli, Walter, and Raul thank you for your patience and time with this.  I finally got it to work!  It turns out I had errors in the way I was coding the params for the datasets.

I have read through the manual regarding Datasets and I have tried to follow the code example that Walter attached to a post earlier in this thread.  Below is the final code that works, would you guys please look it over to see if I have got it correct?  Would be grateful if you would!  I also attached a screen capture showing Form6.

Thanks
TD

<code>
unit Unit6;

interface

uses WebCore, WebForms, WebCtrls, WebData;

type

  TForm6 = class(TForm)
     Label1: TLabel;
     Label2: TLabel;
     Edit2: TEdit;
     Label3: TLabel;
     Edit3: TEdit;
     Edit4: TEdit;
     btnSave: TButton;
     ComboBox1: TComboBox;
     Label5: TLabel;
     ds6: TDataSet;
     ds6B: TDataSet;
     procedure btnSaveClick(Sender: TObject);
     procedure Form6Show(Sender: TObject);
     procedure ds6AfterLoad(Sender: TObject);
     procedure Form6Close(Sender: TObject);
     procedure ds6BAfterLoad(Sender: TObject);
     procedure ds6AfterSave(Sender: TObject);
  private
     { Private declarations }
     procedure AfterCommit(Sender: TObject);
     procedure OnCommitError(Sender: TObject; const ErrorMsg : string);
  public
     { Public declarations }
     dblRandom: double; //public field
     strRandom: string; //public field
     intRandom: integer; //public field
  end;

var
  Form6: TForm6;

implementation

uses unit1, unit7;

procedure TForm6.btnSaveClick(Sender: TObject);
begin
  Form6.dblRandom := Random;
  Form6.strRandom := DoubleToStr(dblRandom);
  Form6.strRandom := strReplace(strRandom,'0.','',True, True);
  Form6.intRandom := strToInt(strRandom);
  Form6.ds6.columns['random_number'].AsInteger := Form6.intRandom;
  Form6.ds6.Save;
end;

procedure TForm6.Form6Show(Sender: TObject);
begin
  Database.Load(ds6);
end;

procedure TForm6.ds6AfterLoad(Sender: TObject);
begin
  Database.StartTransaction;
  Form6.ds6.Insert;
end;

procedure TForm6.Form6Close(Sender: TObject);
begin
  Form7.ShowModal;
end;

procedure TForm6.ds6BAfterLoad(Sender: TObject);

begin
  Form1.LoadDateRange(false);
  Form1.intPID := ds6B.columns['pid'].AsInteger;
  Form6.Close;
end;

procedure TForm6.AfterCommit(Sender: TObject);
begin
 Database.AfterCommit := nil;
 Database.OnCommitError := nil;

  //find pid of record just saved
  Form6.ds6B.params.clear;
  Form6.ds6B.params.add('intRandom='+IntToStr(Form6.intRandom)+'');
  Database.Load(ds6B);
end;

procedure TForm6.OnCommitError(Sender: TObject; const ErrorMsg : string);
begin
 Database.AfterCommit := nil;
 Database.OnCommitError := nil;
 ShowMessage('Error: ' + ErrorMsg);
end;

procedure TForm6.ds6AfterSave(Sender: TObject);
begin
  if Database.InTransaction then
     try
        Database.AfterCommit := AfterCommit;
        Database.OnCommitError := OnCommitError;
        Database.Commit;
     except
        Database.Rollback;
        raise;
     end;
end;

end.

</code>

Anyone?

Thanks,
TD

Perhaps I ask too much.  I really would like to understand this line of code from the master/detail example:

  Database.AfterCommit:=AfterCommit;

What is the "Aftercommit" on the right side of the equals sign?

master/deatil example code:
procedure TOrderEntryDlg.SetupOrder(OrdersDataSet: TDataSet;
                                   IsInserting: Boolean=False);
begin
  Inserting:=IsInserting;
  CancelChecked:=False;
  CommitStarted:=False;
  RollbackStarted:=False;
  Database.BeforeCommit:=BeforeCommit;
  Database.OnCommitError:=CommitError;
  Database.AfterCommit:=AfterCommit;
  Database.BeforeRollback:=BeforeRollback;
  Database.OnRollbackError:=RollbackError;
  Database.AfterRollback:=AfterRollback;
  Orders:=OrdersDataSet;
  OrderIDLabel.DataSet:=Orders;
  OrderDateLabel.DataSet:=Orders;
  PONumberEdit.DataSet:=Orders;
  TermsComboBox.DataSet:=Orders;
  OrderTotalLabel.DataSet:=Orders;
  AmountPaidEdit.DataSet:=Orders;
  BalanceDueLabel.DataSet:=Orders;
  SpecialInstructionsMemo.DataSet:=Orders;
  PurchaseTotalLabel.DataSet:=Orders;
  ShippingTotalLabel.DataSet:=Orders;
  CustomerItems.Params.Clear;
  CustomerItems.Params.Add('OrderID='''+Orders.Columns['OrderID'].AsString+'''');
  Database.Load(CustomerItems);


Thanks,
TD

TD wrote:

Perhaps I ask too much.  I really would like to understand this line of code from the master/detail example:

  Database.AfterCommit:=AfterCommit;

What is the "Aftercommit" on the right side of the equals sign?




See orderentry form - declared in Private section:


    procedure AfterCommit(Sender: TObject);


procedure TOrderEntryDlg.AfterCommit(Sender: TObject);
begin
  Close;
end;


Walter

On 12/29/2014 10:58 AM, TD wrote:
> Perhaps I ask too much.  I really would like to understand this line of code from the master/detail example:

Christmas week is slow anyways and without full project people would
need to create a project and paste your code and make it work so ...

>     Database.AfterCommit:=AfterCommit;
> What is the "Aftercommit" on the right side of the equals sign?

It's a function you defined that you wish to get called by built-in
database object for AfterCommit event.

It has to be defined as per docs :
http://www.elevatesoft.com/manual?action=viewevent&id=ewb1&comp=TDatabase&event=AfterCommit

Basically just a function with Sender:TObject as only argument.

It's the same thing as any event (control OnChange, form OnShow, etc)
except you're assigning it in code (as there is no IDE component for EWB
default Database object).


Better example might be not not use same name so if you defined a
procedure like this :

procedure TOrderEntryDlg.MyCustomAfterCommit(Sender: TObject);
begin
 //do whatever it needs to do in AfterCOmmit
end;

and then the code when setting this up would be

Database.AfterCommit:=MyCustomAfterCommit;


Raul