Change databases Aliases

rbuser

Hi,

I use an application similar to Demo End User -> Report Explorer and users
can edit reports stored in DB.

On aplication start, user select the database alias for database files but
reports is
generated with the database aliases used on this creation.

How to change database alias BEFORE report is processed ?

Any help ?

Samuel

nicocizik

Hi Samuel,

If you are referencing the database alias rather than the TDatabase object,
you will need to change this using the template event OnLoadEnd. From there
you will need to extract the SQL object and change the database alias as you
need.

Check out the following articles.

----------------------------------------------
Tech Tip: Using Template Events
----------------------------------------------

The Report.Template object has several events that can be used for
customizing what happens when a report is loaded or saved:

- OnLoadStart
- OnLoadEnd
- OnNew
- OnSaveStart
- OnSaveEnd


The OnLoadEnd and OnNew events are often used to perform actions related
to report and data initialization.

The OnSaveEnd event is often used to save additional descriptive
("meta") data to the database each time the report is saved.

Example:

The Report.Template events are public and therefore must be assigned at
run-time.


1. In the private section of your form declaration you can declare an
event-handler method:

TForm = class(TForm)
private
procedure myTemplateOnLoadEndEvent(Sender: TObject);

public

end;


2. In the Form.OnCreate event, you can assign the event-handler to the
event:

procedure TForm1.FormCreate(Sender: TObject);
begin

ppReport1.Template.OnLoadEnd := myTemplateOnLoadEndEvent;

end;


3. Implement the event-handler method:

procedure TForm1.myTemplateOnLoadEndEvent(Sender: TObject);
begin

{add code here to initial the report or data, etc. }
ppReport1.PrinterSetup.MarginTop := 0.5;

end;



-------------------------------------------------
Tech Tip: How to access the SQL object associated
with a Report created using DADE
-------------------------------------------------

TdaSQL is a class defined in daQClass.pas.
TdaSQL has a run-time interface for adding search Criteria,
etc. For an example see the EndUser\Custom DataViews example.

OR you can assign its SQLText property. Please note that
once you directly assign the SQLText property the Query tool
buttons such as Sort, Search can no longer be used.



uses
daDatMod;


function GetSQLObject(aReport: TppReport; var aSQL: TdaSQL): Boolean;
var
lDataModule: TdaDataModule;
lDataView: TdaDataView;
begin

aSQL := nil;

{get the datamodule}
lDataModule := daGetDataModule(aReport);

if (lDataModule <> nil) then
begin
lDataView := lDataModule.DataViews[0];

if (lDataView <> nil) and (lDataView is TdaQueryDataView) then
aSQL := TdaQueryDataView(lDataView).SQL;

end;

Result := (aSQL <> nil);

end;


--
Tech Support mailto:support@digital-metaphors.com
Digital Metaphors http://www.digital-metaphors.com

Once you've retrieved the SQL object, you can do something useful to it,
like adding criteria values:

procedure ppReport1BeforePrint(Sender: TObject);
var
lSQL: TdaSQL;
lFields: TStringList;
lCriteria: TdaCriteria;
liIndex: Integer;
begin

{get SQL object}
lSQL := GetSQLObject(ppReport1);

{if criteria have not been created, then add them}
if (lSQL.CriteriaCount = 0) then
begin
{get all available criteria fields}
lFields := TStringList.Create;

lSQL.AvailableCriteriaList(lFields);

{set string list entries to field names}
for liIndex := 0 to lFields.Count - 1 do
lFields[liIndex] := TdaField(lFields[liIndex]).FieldName;

{create order no criteria}
liIndex := lFields.IndexOf('OrderNo');

if (liIndex <> -1) then
begin
lCriteria := lSQL.SelectCriteria(liIndex);
lCriteria.Operator := dacoEqual;
end;

{create art code criteria}
liIndex := lFields.IndexOf('ArtCode');

if (liIndex <> -1) then
begin
lCriteria := lSQL.SelectCriteria(liIndex);
lCriteria.Operator := dacoEqual;
end;

{create begin/end date criteria}
liIndex := lFields.IndexOf('OrderDate');

if (liIndex <> -1) then
begin
lCriteria := lSQL.SelectCriteria(liIndex);
lCriteria.Operator := dacoBetween;
end;

lFields.Free;
end;

{set order no. search value}
lSQL.Criteria[0].Value := '1020';

{set art code search value}
lSQL.Criteria[1].Value := 'C';

{set begin/end date search value}
lSQL.Criteria[2].Value := '31/12/90,31/12/99';

end;

--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com