delphi DBGrid cell not empty - database

Question

In my form, i have a TDBGRid, TDatasource , MessageTable and 2 button. I have a button to add new row in my DBGRID :
MessageTable.Append;
MessageTable.Edit;
MessageTable.FieldByName('FieldName').AsString := sName;
MessageTable.Post;
The second button is used to delete a current row :
MessageTable.Edit ;
MessageTable.Delete ;
How can ensure all Cell not empty before the post?
If there is an empty Cell, i need to ignore this row !
how can I do that?

Answer 1

You should use the features the dataset (in this case, TTable) already give you instead of trying to reinvent the wheel. TDataSet provides an event (OnBeforePost) that is specifically designed for this purpose.
Click on your TTable, and then switch to the Events tab in the Object Inspector. Find the OnBeforePost event and double click it to generate the event shell in the Code Editor. You'll see something like this:
procedure TForm1.Table1BeforePost(DataSet: TDataSet);
begin
// DataSet is the TDataSet (TTable, TQuery, TADOQuery, etc.) to which
// event is attached
end;
You can do all of your validations needed before a record is actually written to the database here. For instance, if you want to make sure every single field has something in it, you can do this:
procedure TForm1.Table1BeforePost(DataSet: TDataSet);
var
i: Integer;
begin
// You can replace DataSet with your actual table variable name, but using it
// this way allows you to use this same event for more than one table if you want.
for i := 0 to DataSet.FieldCount - 1 do
if DataSet.Fields[i].IsNull then
raise Exception.CreateFmt('Field %s has no value', DataSet.Fields[i].FieldName);
end;
If you want to make sure only certain fields have values, or that the value is within a certain range, you can access the field directly:
procedure TForm1.Table1BeforePost(DataSet: TDataSet);
begin
if DataSet.FieldByName('MyField').IsNull then
Abort; // This silently cancels the post without telling the user
if DataSet.FieldByName('AField').AsInteger = 0 then
raise Exception.Create('AField must not be 0');
end;
Now you don't have to do anything at all in your TDBGrid. If the user hits DownArrow on the last row and a new row is inserted, and they enter incomplete or wrong data, the events above will take care of it. They'll also work if you use two buttons (one to insert or edit and the other to post), because the events will handle everything else.
procedure TForm1.ButtonInsertClick(Sender: TObject);
begin
Table1.Insert; // Or Append - if you have an index on the table they're the same thing
end;
procedure TForm1.ButtonPostClick(Sender: TObject);
begin
Table1.Post; // This is 100% of the code you need here
end;