Combobox1.Items.AddObject(....)

[Henry Olive 5]

Good Day,

 

I add Customer No & Customer Name in a combobox like below

Combobox1.Items.AddObject(SQLQuery1.Fields[1].asString,  Pointer(SQLQuery1.Fields[1].asInteger));

I want to make CutNo=1  record in the combobox selected  (I mean, combobox1.text = CustNo=1 record's Customer Name)

but i get,   Identifier expected but 'OBJECT' found error msg.
Combobox1.ItemIndex := Integer(Combobox1.Items.Object[Combobox1.ItemIndex]);

Could someone please help

Thank You

 

Edited March 20, 2023 by Henry Olive

[Lajos Juhász 293]

I think this is a very bad idea. You code doesn't compiles as you're missing a letter s, the property nam is objects:

 

 Combobox1.ItemIndex := Integer(Combobox1.Items.Objects[Combobox1.ItemIndex]);

[DelphiUdIT 176]

1 hour ago, Henry Olive said:

Combobox1.ItemIndex := Integer(Combobox1.Items.Object[Combobox1.ItemIndex]);

 

43 minutes ago, Lajos Juhász said:

I think this is a very bad idea. You code doesn't compiles as you're missing a letter s, the property nam is objects:

Combobox1.ItemIndex := Integer(Combobox1.Items.Objects[Combobox1.ItemIndex]); 

 

 

May be you mean:

 

var tempointer: Pointer;
tempointer := Combobox1.Items.Objects[Combobox1.ItemIndex];
Combobox1.ItemIndex := Integer(tempointer^);

 But even if this is correct, the starting point is incorrect:

 

1 hour ago, Henry Olive said:

Combobox1.Items.AddObject(SQLQuery1.Fields[1].asString,  Pointer(SQLQuery1.Fields[1].asInteger));

PAY ATTENTION: SqlQuery1 I think dynamically allocates Fields[1] and therefore your POINTER will be invalid after a new QUERY is executed.

The pointer used with the AddObjects function should be permanent and "last" for the entire existence of the program (until you know what you are doing )
 

Bye

Edited March 20, 2023 by DelphiUdIT

[Lajos Juhász 293]

2 hours ago, DelphiUdIT said:

PAY ATTENTION: SqlQuery1 I think dynamically allocates Fields[1] and therefore your POINTER will be invalid after a new QUERY is executed.

You should read the code: SQLQuery1.Fields[1].asInteger integer value of the field converted to a pointer.

 

The problem here is that the id is not going to be a continous enumeration starting from 0.

[programmerdelphi2k 237]

try some like this:

• NOTE:   TObject( 0 ) = NIL

type
  TForm1 = class(TForm)
    ListBox1: TListBox;
    Button1: TButton;
    Button2: TButton;
    Memo1: TMemo;
    FDMemTable1: TFDMemTable;
    FDMemTable1MyID: TIntegerField;
    FDMemTable1MyText: TStringField;
    procedure Button1Click(Sender: TObject);
    procedure ListBox1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  // 0..10
  // for var i: integer := 0 to 10 do
  // ListBox1.AddItem('Item' + i.ToString, TObject(i));
  //
  // FDMemTable
  FDMemTable1.First;
  //
  while not FDMemTable1.Eof do
    begin
      ListBox1.AddItem(FDMemTable1MyText.AsString, TObject(FDMemTable1MyID.AsInteger)); // Warning: TObject( 0 ) = nil
      //
      FDMemTable1.Next;
    end;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  i: integer;
begin
  { 0..10
    i := (ListBox1.Count - 1);
    //
    if (i < 0) then
    exit;
    //
    i := random(i);
    //
    ListBox1.ItemIndex := integer(ListBox1.Items.Objects[i]);
  }
  // -------------------
  // FDMemTable
  i := (ListBox1.Items.Count - 1);
  i := random(i);
  //
  Memo1.Lines.Add(i.ToString);
  //
  if (ListBox1.Items.Objects[i] = nil) then // ...Objects[ 0 ] = nil
    begin
      Memo1.Lines.Add('nil');
      i := -1;  //  == "0"
    end
  else
    i := ListBox1.Items.IndexOfObject(ListBox1.Items.Objects[i]);
  //
  ListBox1.ItemIndex := i;
end;

procedure TForm1.ListBox1Click(Sender: TObject);
begin
  if (ListBox1.ItemIndex > -1) then
    Caption := integer(ListBox1.Items.Objects[ListBox1.ItemIndex]).ToString;
end;

initialization

ReportMemoryLeaksOnShutdown := true;

end.

 

  

    

Edited March 20, 2023 by programmerdelphi2k

[programmerdelphi2k 237]

procedure TForm1.Button3Click(Sender: TObject);
var
  x: TObject;
begin
  x := TObject(0); //1...
  //
  if x = nil then
    ShowMessage('nil')
  else
    ShowMessage('not nil');
end;

 

[David Schwartz 426]

9 hours ago, Henry Olive said:

Good Day,

 

I add Customer No & Customer Name in a combobox like below

Combobox1.Items.AddObject(SQLQuery1.Fields[1].asString,  Pointer(SQLQuery1.Fields[1].asInteger));
 

 

Since the same field value (a numerical string) is being used in both places, all this code is doing is saving you a StrToInt conversion later one, and it's not necessary.

 

It makes me think ... who in their right mind would put a bunch of numbers into a ComboBox? I'm guessing you have oversimplified your example. But perhaps not.

 

Assuming not, and given that the ComboBox just has a bunch of numerical strings in it, you just need to say, "Combobox1.Text.AsInteger" to get its numerical VALUE ... when you need it.

Why waste memory by doing the conversion earlier and sticking it into the Obect's array?

 

Besides, the values in Objects are NOT Pointers, they're references to TObject instances. So you should cast them to TObjects, not Pointers. That still doesn't make much sense to me.

 

Doesn't the basic TComboBox allow Names and Values to be specified? Or is that just the Raize version? Because that's what I'd use. (If not, then I'd use name=value pairs and a custom OnShow method to only display the Name part and then extract the Value part in the OnSelect handler.)
 

Edited March 20, 2023 by David Schwartz

[Henry Olive 5]

Thank you so much Lajos, DelphiUdit, Programmer, David

 

David,  Combobox1.Text.AsInteger doesnt compile in D10.3

[Stano 143]

StrtToInt()

[David Schwartz 426]

On 3/21/2023 at 4:12 AM, Henry Olive said:

 

David,  Combobox1.Text.AsInteger doesnt compile in D10.3

As Stano said ... there's always StrToInt( Combobox1.Text )