working with a dataset from other form?
lazarus / 16-Databases

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tatamata · 2007-09-02 07:25

Hello.
I have a Firebird database and want to use it as embedded database
with Lazarus. As in embedded case there can't be several simultaneous
connections to the database, obviously I must put connection component
to the main form and use it from other forms. I put also all dataset
components to the main form, while datasource components put on the
secondary forms. Before opening some other form with for example
datagrids, I set Dataset property of the Datasource component
programatically from the main form, and it works. Main form has other
form's units in it's Uses part.
But, what to do when I need to programatically access dataset object
in the main form, from other forms? I can't put main form's unit in
the uses of the secondary form, because circular reference is not
allowed. Therefore I tried to use Dataset property of the datasource
in order to reach dataset in the main form. But it doesn't accept some
properties of the Dataset. For example, this works:
with Datasource1.Dataset do begin
    Active:=True;  
but this doesn't:
with DatasourceDestinationTable.Dataset do begin
    TableName:='TBL1';
    Active:=True;
end; 
It doesn't accept TableName property ofthe dataset object from the
main form.

Also, I can't assign new sql string to ZQuery component in the main
form:
  with DatasourceZQueryTemp.DataSet.SQL do begin
    Clear;
    Add('DELETE FROM TBL1');
    ExecSQL;
  end;

So, how to access and work with datasets of the main form, from a
secondary form?

Regards,

Zlatko

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tatamata · 2007-09-13 12:59

Ok. I will answer to myself.
While crossreferencing of units is not allowed in interface part, it
is allowed in implementation part.