Delphi TTreeNode recursively append child nodes to parent node - delphi

Question

I have an assignment in "project management". I have to assign modules which can also be sub-modules, so I want to append recursively sub-modules to modules.
Example:
P(project) Modules(M1,M2,M3,M4). Under M1 Module there will be sub-modules(M1S1,M1S2,M1S3), and under sub-module1 (M1S1) there can be many sub-modules (M1S1S1, M1S1S2, M1S1S3) and so on.
I have done this code using Recursion and TTreeNode but i feel the problem is with condition statement.
procedure TForm2.BitBtn1Click(Sender: TObject);
begin
lGlblProjID := 1;
lGlblProjName := 'Project';
ADOConnectionListner.Connected := true;
try
if ADOConnectionListner.Connected then
begin
RootNode := TreeView2.Items.Add(nil, lGlblProjName);
getSubChild(lGlblProjID, RootNode);
end;
except
on E: Exception do
begin
ShowMessage('Exception Class = ' + E.ClassName);
end;
end;
end;
procedure TForm2.getSubChild(var Pid: Integer; var SubRoot: TTreeNode);
var
lcount, I, lcurrentID: Integer;
lcurrentName: String;
lModuleNode: TTreeNode;
begin
// ShowMessage(IntToStr(Pid)+ ' '+SubRoot.Text);
ADOQuery1.SQL.Clear;
ADOQuery1.SQL.Add('SELECT * FROM treetab Where parent_id =:value1');
ADOQuery1.Parameters.ParamByName('value1').Value := Pid;
ADOQuery1.Active := true;
lcount := ADOQuery1.RecordCount;
for I := 0 to lcount - 1 do
begin
lcurrentID := ADOQuery1.FieldByName('id').AsInteger;
lcurrentName := ADOQuery1.FieldByName('name').AsString;
ShowMessage(' id ' + IntToStr(lcurrentID) + ' dd ' + lcurrentName); // print valu of i
if ((lcurrentID <> 0)and (SubRoot.Text <> '') ) then //or
begin
lModuleNode := TreeView1.Items.AddChild(SubRoot, lcurrentName);
getSubChild(lcurrentID, lModuleNode);
end else // if
// lcurrentID = 0
ShowMessage('end reached');
// TreeView1.Items.AddChild(SubRoot, ADOQuery1.FieldByName('name').AsString);
ADOQuery1.Next;
//*********
end;
end;
I want to retrieve all the sub-modules for a particular project like in this case project with id=1 only.

Answer 1

Your problem seems to be the non-local ADOQuery1 which gets cleared at entry on each recursive call. Therefore you loose all remaining records from a previous query. You should arrange a local storage for the query results.
Something like (untested):
procedure GetSubChild()
type
TTempRecord = record
id: integer;
name: string;
end;
TTempArray = array of TTempRecord;
var
lcount, I, lcurrentID: Integer;
lcurrentName: String;
lModuleNode: TTreeNode;
recs: TTempArray
begin
// ...
// query the db
// ...
lcount := ADOQuery1.RecordCount;
SetLength(recs, lcount);
for i := 0 to lcount-1 do
begin
recs[i].id := ADOQuery1.FieldByName('id').AsInteger;
recs[i].name := ADOQuery1.FieldByName('name').AsString;
ADOQuery1.Next;
end;
for i := 0 to lcount-1 do
begin
lcurrentID := recs[i].id;
lcurrentname := recs[i].name;
// ...
// add to treeview
// call recursively GetSubChild()
// ...
end;
end;