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9.7

Delete a record in a database.

Asked by peterkiers in Delphi Programming

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
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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.
[+][-]09/01/09 07:28 PM, ID: 25237751Accepted Solution

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Solution Provided By: EddieShipman
Participating Experts: 2
Solution Grade: A
 
[+][-]09/01/09 11:58 PM, ID: 25238494Expert Comment

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