Get currently selected Combobox value and use it as variable

Question

My question is about Delphi 7.

I need to get currently selected ComboBox1 value to use it as Floating point variable in my code:

t:=t+ComboBox1. // Not sure what to write here...

Thank you!

TLama · Accepted Answer · 2011-11-19T12:39:07.400

11

Not sure if the TryStrToFloat is already in Delphi 7, but if yes I would do it this way.

procedure TForm1.ComboBox1Change(Sender: TObject);
var
  Value: Double;
begin
  if TryStrToFloat(ComboBox1.Text, Value) then
    T := T + Value
  else
    ShowMessage('You''ve entered wrong value ...');
end;

edited Nov 19 '11 at 12:39

answered Nov 19 '11 at 12:30

TLama

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1

Worked and was exactly what I needed! – enflam3 Nov 19 '11 at 12:47
1

Hm, didn't know about `TryStrToFloat()`, although I always used `StrToFloatDef()` which is in the same unit (SysUtils). +1 – binar Dec 21 '11 at 21:36
@talereader, thanks. Btw. both functions, [`TryStrToFloat`](http://docwiki.embarcadero.com/VCL/en/SysUtils.TryStrToFloat) and [`StrToFloatDef`](http://docwiki.embarcadero.com/VCL/en/SysUtils.StrToFloatDef) internally calls the [`TextToFloat`](http://docwiki.embarcadero.com/VCL/en/SysUtils.TextToFloat) function. The only difference is how do they use it; if you write e.g. `var Output: Extended; begin if not TryStrToFloat('0.xx', Output) then Output := 0.01; end;` then you will get the same as if you call `Output := StrToFloatDef('0.xx', 0.01);` ;) – TLama Dec 21 '11 at 21:49

splash · Answer 2 · 2011-11-19T18:52:59.060

5

// ItemIndex is the index of the selected item
// If no item is selected, the value of ItemIndex is -1
if (ComboBox1.ItemIndex >= 0) then
begin
  t := t + StrToFloat(ComboBox1.Items[ComboBox1.ItemIndex]);
end;

edited Nov 19 '11 at 18:52

answered Nov 19 '11 at 12:22

splash

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Or better [TryStrToFloat](http://docwiki.embarcadero.com/VCL/en/SysUtils.TryStrToFloat) and you can use `ComboBox1.Text` instead of `ComboBox1.Items[ComboBox1.ItemIndex])` – TLama Nov 19 '11 at 12:25
There is one extra ")" in the code. After Removing it, it worked just fine. Thank you! – enflam3 Nov 19 '11 at 12:50
Personally I don't like this code because it uses two references to the ComboBox1.ItemIndex property. I am not sure what the read method for this property does, maybe it just reads a field so there is no performane penalty, but it just feels wrong. – dummzeuch Nov 19 '11 at 16:06
3

@TLama: accessing ComboBox1.Text is *not* the same as ComboBox1.Items[ComboBox1.ItemIndex]). It is possible for the text to not be in the Items list. – dummzeuch Nov 19 '11 at 16:07

score 1 · Answer 3 · answered Mar 30 '19 at 16:56

1

In Delphi 10.2 Tokyo i just do:

[string] := ComboBox.Selected.Text

answered Mar 30 '19 at 16:56

Rodrigues2099

31
3

This answer is not helpfull to the question that already has been answered. – Vulpex Mar 30 '19 at 17:17

score 0 · Answer 4 · answered Aug 31 '23 at 14:51

0

Nowadays it is ComboBox1.Text; only :)

answered Aug 31 '23 at 14:51

Dreamer64

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Get currently selected Combobox value and use it as variable

4 Answers4