Question

Delete a record in a database.

Asked by: peterkiers

I have made a little programm that has a Treeview, a RichEdit.
and 4 buttons on a Panel. 2 buttons are for loading and saving
the treeview nodes with its associating text on the RichtEdit
to a database. The other 2 buttons are for creating a Folder-node
and a File-node in the Treeview. Everything works perfect.

Now I want to make a fifth button on the panel for deleting
a Treeview node. The procedure is done:

procedure TForm1.DeleteItemClick(Sender: TObject);
var
   node : TTreeNode;
   mess, str : string;
   key_stat : integer;
begin
    Node := Treeview.Selected;
    if Assigned(Node) then
       begin
       str := Node.Text;
       mess := 'Are you sure that you want to delete the';
       Case Node.Level of
         0 : mess := mess + ' folder : ' +#13+#13 + str + '   ???' +#13+
                    'All folders, subfolders, items and subitems' +#13+ 'will be permanently deleted !!' +#13;
         1 : mess := mess + ' item : ' +#13+#13 + str + '   ???' + #13;
       end;
       with Application do
         begin
         NormalizeTopMosts;
         key_stat := MessageBox(pchar(mess), '         Confirmation', MB_YESNO);
         RestoreTopMosts;
       end;
       if key_stat = 7 then  Exit;         // 6 - YES ; 7 - N0
       TreeView.Items.Delete(Treeview.Selected);
       end
    else ShowMessage('Select a folder in the treeview first.');
end;

ACCEPT for one thing: The deleted node is still available in the database!!!
And it should be erased too. That's because the DeleteItemClick should call
for this procedure:

procedure TItem.Delete;
begin
//
end;

Who can help me to solve this problem?
I have put the complete code in the code-section

Thank you in advanced.

Peter Kiers

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, DB, ADODB, ComCtrls, StdCtrls, ImgList, ExtCtrls;
 
type
  TForm1 = class(TForm)
    TreeView1: TTreeView;
    Splitter1: TSplitter;
    Panel1: TPanel;
    Button1: TButton;
    Button2: TButton;
    ADOQuery1: TADOQuery;
    ADOConnection1: TADOConnection;
    FolderBtn: TButton;
    FileBtn: TButton;
    ImageList1: TImageList;
    RichEdit1: TRichEdit;
    Button3: TButton;
    procedure Button3Click(Sender: TObject);
    procedure RichEdit1KeyUp(Sender: TObject; var Key: Word;
      Shift: TShiftState);
    procedure FolderBtnClick(Sender: TObject);
    procedure FileBtnClick(Sender: TObject);
    procedure TreeView1Change(Sender: TObject; Node: TTreeNode);
    procedure FormCreate(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    
  private
    { Private declarations }
    procedure savetree(t: ttreeview);
    procedure loadtree(t: TTreeView);
    procedure saveNode(n: TTreeNode);
    function findNode(t:TTreeView; id: integer): TTreeNode;
    procedure AddItem(aText: string; aIndex: Integer; aParent: TTreeNode);
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
type
  TItem = class(TObject)
  private
    fStatus: byte;
    fParentID: integer;
    fNodeText: string;
    fID: integer;
    fData: string;
    fSaver: TAdoQuery;
    fChanged: Boolean;        
    fSaveImmediate: boolean;
    fIsNew: Boolean;
    fImageIndex: integer;
    procedure SetData(const Value: string);
    procedure SetNodeText(const Value: string);
    procedure SetParentID(const Value: integer);
    procedure SetStatus(const Value: byte);
    procedure SetImageIndex(const Value: integer);
  protected
    procedure Changed; dynamic;
  public
    constructor Create(aSaver: TAdoQuery; AId, AParentID: integer; AStatus: byte);
    constructor LoadFromDataset(aSaver: TAdoQuery);
    procedure BeginUpdate;
    procedure EndUpdate;
    procedure Delete;
    procedure Save;
  published
    property ID: integer read fID write fID;
    property ParentID: integer read fParentID write SetParentID;
    property ImageIndex: integer read fImageIndex write SetImageIndex;
    property Status: byte read FStatus write SetStatus;
    property Data: string read fData write SetData;
    property NodeText: string read fNodeText write SetNodeText;
  end;
 
{ TItem }
 
procedure TItem.BeginUpdate;
begin
  fSaveImmediate := false;                 
end;
(*---------------------------------------------------*)
procedure TItem.Changed;
begin
  fChanged := True;
  if fSaveImmediate then Save;
end;
(*---------------------------------------------------*)
constructor TItem.Create(aSaver: TAdoQuery; AId, AParentID: integer;
  AStatus: byte);
begin
  inherited Create;
  fChanged := False;
  fSaveImmediate := True;
  fIsNew := True;
  fSaver := aSaver;
  fID := AID;
  fParentID := AParentID;
  fStatus := AStatus;
  fNodeText := '';
  fData := '';
end;
(*---------------------------------------------------*)
procedure TItem.Delete;
begin
//
end;
(*---------------------------------------------------*)
procedure TItem.EndUpdate;
begin
  fSaveImmediate := True;
  if fChanged then Save;
end;
(*---------------------------------------------------*)
constructor TItem.LoadFromDataset(aSaver: TAdoQuery);
begin
  Create(aSaver, 0, 0, 0);
  if not aSaver.IsEmpty then
  begin
    fId := aSaver.FieldByName('ID').AsInteger;
    fParentID := aSaver.FieldByName('PARENT').AsInteger;
    fStatus := aSaver.FieldByName('STATUS').AsInteger;
    fNodeText := aSaver.FieldByName('NAME').AsString;
    if aSaver.FindField('DATA') <> nil then
      fData := aSaver.FieldByName('DATA').AsString;
    fImageIndex := aSaver.FieldByName('IMAGE_INDEX').AsInteger;
    fIsNew := False;
  end;
end;
(*---------------------------------------------------*)
procedure TItem.Save;
begin
  if fIsNew then
    fSaver.SQL.Text :=
      'insert into tree (parent, name, status, image_index, data) values (:v1, :v2, :v3, :v4, :v5)'
  else
    fSaver.SQL.Text :=
      'update tree set parent = :v1, name = :v2, status = :v3, image_index = :v4, data = :v5 where id = :v6';
  fSaver.Parameters.ParamByName('v1').Value := fparentID;
  fSaver.Parameters.ParamByName('v2').Value := fNodeText;
  fSaver.Parameters.ParamByName('v3').Value := fStatus;
  fSaver.Parameters.ParamByName('v4').Value := fImageIndex;
  fSaver.Parameters.ParamByName('v5').Value := fData;
  if not fIsNew then
    fSaver.Parameters.ParamByName('v6').Value := fId;
  fSaver.ExecSQL;
  if fIsNew then
  begin
    fSaver.SQL.Text :=
      'SELECT id from tree order by id desc';
    fSaver.Open;
    fId := fSaver.FieldByName('ID').asInteger;
    fSaver.Close;
    fIsNew := False;
  end;
  fChanged := False;
end;
(*---------------------------------------------------*)
procedure TItem.SetData(const Value: string);
begin
  if fData <> Value then
  begin
    fData := Value;
    Changed;
  end;
end;
(*---------------------------------------------------*)
procedure TItem.SetImageIndex(const Value: integer);
begin
  if fImageIndex <> Value then
  begin
    fImageIndex := Value;
    Changed;
  end;
end;
(*---------------------------------------------------*)
procedure TItem.SetNodeText(const Value: string);
begin
  if fNodeText <> Value then
  begin
    fNodeText := Value;
    Changed;
  end;
end;
(*---------------------------------------------------*)
procedure TItem.SetParentID(const Value: integer);
begin
  if fParentId <> Value then
  begin
    fParentID := Value;
    Changed;
  end;
end;
(*---------------------------------------------------*)
procedure TItem.SetStatus(const Value: byte);
begin
  if fStatus <> Value then
  begin
    FStatus := Value;
    Changed;
  end;
end;
(*---------------------------------------------------*)
procedure TForm1.AddItem(aText: string; aIndex: Integer; aParent: TTreeNode);
var n: TTreeNode;
  data: TItem;
  parentId: integer;
begin
  parentId := 0;
  if (aParent <> nil) and (TItem(aParent.Data) <> nil) then
    parentId := TItem(aParent.Data).ID;
  data := TItem.Create(AdoQuery1, -1, parentId, 0);
  data.NodeText := aText;
  data.ImageIndex := aIndex;
  n := TTreeNode.Create(TreeView1.Items);
  n.Text := data.NodeText;
  n.ImageIndex := data.ImageIndex;
  n.SelectedIndex := data.ImageIndex;
  TreeView1.Items.AddNode(n, aParent, aText, data, naAddChild);
end;
(*---------------------------------------------------*)
procedure TForm1.Button1Click(Sender: TObject);
begin
  loadTree(treeview1);
end;
(*---------------------------------------------------*)
procedure TForm1.Button2Click(Sender: TObject);
begin
  savetree(treeview1);
end;
procedure TForm1.Button3Click(Sender: TObject);
var
   node : TTreeNode;
   mess, str : string;
   key_stat : integer;
begin
    Node := Treeview1.Selected;
    if Assigned(Node) then
       begin
       str := Node.Text;
       mess := 'Are you sure that you want to delete the';
       Case Node.Level of
         0 : mess := mess + ' folder : ' +#13+#13 + str + '   ???' +#13+
                    'All folders, subfolders, items and subitems' +#13+ 'will be permanently deleted !!' +#13;
         1 : mess := mess + ' item : ' +#13+#13 + str + '   ???' + #13;
       end;
       with Application do
         begin
         NormalizeTopMosts;
         key_stat := MessageBox(pchar(mess), '         Confirmation', MB_YESNO);
         RestoreTopMosts;
       end;
       if key_stat = 7 then  Exit;         // 6 - YES ; 7 - N0
       TreeView1.Items.Delete(Treeview1.Selected);
       end
    else ShowMessage('Select a folder in the treeview first.');
end;
(*---------------------------------------------------*)
procedure TForm1.FileBtnClick(Sender: TObject);
var aText: string;
begin
  if (TreeView1.Selected <> nil) and (TreeView1.Selected.ImageIndex = 15) then
  begin
     if InputQuery('File', 'Enter a file name', aText) then
      AddItem(aText, 17, TreeView1.Selected);
  end else
    ShowMessage('Select a folder in the treeview first.');
end;
(*---------------------------------------------------*)
function TForm1.findNode(t: TTreeView; id: integer): TTreeNode;
var i:integer;
begin
  i:=0;
  while (i<t.items.count) and (TItem(t.items[i].data).ID<>id) do
    inc(i);
  if i<t.items.count then result:=t.items[i]
                     else result:=nil;
end;
(*---------------------------------------------------*)
procedure TForm1.FolderBtnClick(Sender: TObject);
var aText: string;
  aParent: TTreeNode;
begin
  aParent := nil;
  if TreeView1.Selected <> nil then
  begin
    if TreeView1.Selected.ImageIndex = 15 then
      aParent := TreeView1.Selected
    else
    begin
      ShowMessage('Select a folder first');
      Exit;
    end;
  end;
  if InputQuery('Folder', 'Enter a folder name', aText) then
    AddItem(aText, 15, aParent);
end;
(*---------------------------------------------------*)
procedure TForm1.FormCreate(Sender: TObject);
var
  conn_str:string;
begin
  conn_str:='provider=Microsoft.Jet.OLEDB.4.0;Persist Security Info=False;Data Source=';
  conn_str:=conn_str+IncludeTrailingPathDelimiter(ExtractFilePath(Application.Exename));
  conn_str:=conn_str+'test.pkd;';
  ADOConnection1.Connected:=False;
  ADOConnection1.ConnectionString:=conn_str;
  ADOConnection1.Connected:=True;
  ADOConnection1.Open;
end;
(*---------------------------------------------------*)
procedure TForm1.loadtree(t: TTreeView);
var
  p, n: TTreeNode;
  data: TItem;
begin
  t.Items.Clear;
  ADOQuery1.SQL.Text := 'select * from tree order by parent asc';
  ADoQuery1.Open;
  while not ADoQuery1.Eof do
  begin
    data := TItem.LoadFromDataset(AdoQuery1);
    p := FindNode(t, data.ParentID);
    n := t.items.AddChildObject(p, data.NodeText, data);
    n.ImageIndex := data.ImageIndex;
    n.SelectedIndex := data.ImageIndex;
    AdoQuery1.Next;
  end;
  AdoQuery1.Close;
end;
(*---------------------------------------------------*)
procedure TForm1.saveNode(n: TTreeNode);
var i, aParent: integer;
  item: TItem;
begin
  item := TItem(n.Data);
  if item <> nil then
  begin
    item.BeginUpdate;
    try
      Item.NodeText := n.Text;
      aParent := 0;
      if (n.Parent <> nil) and (TItem(n.Parent.Data) <> nil) then
        aParent := TItem(n.Parent.Data).ID;
      Item.ParentID := aParent;
      Item.ImageIndex := n.ImageIndex;
    finally
      Item.EndUpdate;
    end;
  end;
  for i := 0 to n.Count-1 do SaveNode(n.Item[i]);
end;
(*---------------------------------------------------*)
procedure TForm1.savetree(t: ttreeview);
var n: TTreeNode;
begin
  n := t.items.getFirstNode;
  while n <> nil do
  begin
    SaveNode(n);
    n := n.getNextSibling;
  end;
end;
(*---------------------------------------------------*)
procedure TForm1.TreeView1Change(Sender: TObject; Node: TTreeNode);
begin
  RichEdit1.Text := '';
  if (Node <> nil) and (Node.ImageIndex = 15) then
    RichEdit1.Text := TItem(Node.Data).Data;
end;
(*---------------------------------------------------*)
procedure TForm1.RichEdit1KeyUp(Sender: TObject; var Key: Word;
  Shift: TShiftState);
  var n: TTreeNode;
begin
        n := TreeView1.Selected;
        if (n <> nil) and (n.ImageIndex = 15) then
        begin
        TItem(n.Data).fSaveImmediate := False;
         TItem(N.Data).Data := RichEdit1.Text;
         end;
end;
(*---------------------------------------------------*)
end.

                                  
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Asked On
2009-09-01 at 01:48:19ID24697285
Topic

Delphi Programming

Participating Experts
2
Points
500
Comments
11

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by: EddieShipmanPosted on 2009-09-01 at 19:28:38ID: 25237751

Ok, what you want to do is get the id from the Data property of the selected item BEFORE it is deleted in the DeleteItemClick and then use the SQL

DELETE FROM tree WHERE id = :id

and pass the id as the parameter and ExecSQL the above.

 

by: Geert_GruwezPosted on 2009-09-01 at 23:58:30ID: 25238494

there would be 2 types of delete ...
delete 1 node and all the decendants will complain there parent is missing
or
delete all decendants starting with the last child and working up

procedure TItem.FindAllDecendants(aId: integer; List: TStrings);
var Parents, Children: TStrings;
  qry: TAdoQuery;
  I: integer;
begin
  Parents := TStringList.Create;
  try
    Children := TStringList.Create;
    try
      Children.Add(IntToStr(aId));
      qry := TAdoQuery.Create(fSaver.Owner); 
      try
        qry.Connection := fSaver.Connection;
        qry.SQL.Text := 'SELECT ID FROM TREE WHERE PARENT = :PARENTID';
        repeat
          Parents.Assign(Children);
          Children.Clear;
          for I := 0 to Parents.Count-1 do
          begin
            qry.Close;
            qry.Parameters.ParamByName('PARENTID').Value := Parents[I];
            qry.Open;
            while not qry.Eof do 
            begin
              Children.Add(qry.FieldByName('ID').AsString);
              qry.Next;
            end;
            qry.Close;
          end;
          List.AddStrings(Children);
        until Children.Count = 0;
      finally
        qry.Free;
      end;
    finally
      Children.Free;
    end;    
  finally
    Parents.Free;
  end;  
end;
 
procedure TItem.DeleteAllDecendants(aId: integer);
var List: TStrings;
  qry: TAdoQuery;
  I: integer;
begin
  List := TStringList.Create;
  try
    FindAllDecendants(aId, List);
    if List.Count > 0 then 
    begin
      qry := TAdoQuery.Create(fSaver.Owner); 
      try
        qry.Connection := fSaver.Connection;
        qry.SQL.Text := 'DELETE FROM TREE WHERE ID = :ID';
        for I := List.Count-1 downto 0 do 
        begin
          qry.Parameters.ParamByName('ID').Value := List[I];
          qry.ExecSQL;
        end;
        // You could delete the node itself here too
        // by uncommenting following 2 lines
        (*
        qry.Parameters.ParamByName('ID').Value := aId;
        qry.ExecSQL;
        *)
      finally
        qry.Free;
      end;
    end;    
  finally
    List.Free;
  end;  
end;
                                              
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by: peterkiersPosted on 2009-09-02 at 08:44:24ID: 25242288

Eddy I like your solution, but I am not able to do it myself.
Could you help me and give me an example?

Greetings, Peter Kiers

 

by: EddieShipmanPosted on 2009-09-02 at 11:04:25ID: 25243775

Will try to this afternoon.

 

by: Geert_GruwezPosted on 2009-09-02 at 11:33:10ID: 25244085

i don't get this
i thought you would have found the next simple step yourself ...
if you delete a node without checking for children you will get problems in the future with your data

put some effort into it !
or go to GetACoder.com and pay for a custom built app
this site is for helping people with problems, not providing complete apps free of charge

procedure TItem.Delete;
begin
  DeleteAllDescendants(ID);
end;

                                              
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by: Geert_GruwezPosted on 2009-09-02 at 16:26:14ID: 25246648

if you want a complete app and not program anything ...
go to www.gexperts.org
install that (it will be in your Delphi version)

then go the gexperts menu and look for code librarian
this is exactly what you are programming

you can even download the code from that site

 

by: peterkiersPosted on 2009-09-03 at 01:19:04ID: 25248699

I want to wait for EddyShipman's solution.

Greetings, Peter Kiers

 

by: Geert_GruwezPosted on 2009-09-03 at 01:22:09ID: 25248710

uh, yeah, right
check line 56 from http://#25238494
and line 60

any particular reason why you want to ignore solution http://#25238494 ?

 

by: peterkiersPosted on 2009-09-03 at 01:32:42ID: 25248765

Yes, your right your solution was the right answer.

Greetings, Peter Kiers

 

by: EddieShipmanPosted on 2009-09-03 at 06:32:50ID: 25250449

I will contact Netminder to have him switch answers.

E.

 

by: Geert_GruwezPosted on 2009-09-03 at 06:49:14ID: 25250608

Nah... leave it at that.
E-> you deserve credit for starting the first comment

20120131-EE-VQP-002

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