"Can't take the address of constant expressions"

[Jvan]

I coded this:

Code: Pascal  [Select][+][-]

1. procedure TfrmMain.txtMovMntDChange(Sender: TObject);
2. var
3.   myfloat: double;
4. begin
5.   if not(TryStrToFloat(txtMovMntD.Text, myfloat)) then begin
6.     SetLength(txtMovMntD.Text, Length(txtMovMntD.Text) - 1);
7.     ShowMessage('Debe ingresar un monto válido.');
8.   end;
9. end;
10.  

But I got this error message: "Can't take the address of constant expressions".
I'm trying to validate that the user wrote a float number, and remove the last character if not.

[Warfley]

Text is a property, not a variable. SetLength only works on variables. You can get a valua via the property and set a value to it, so one Alternative could be:

Code: Pascal  [Select][+][-]

1. txtMovMntD.Text := txtMovMntD.Text.Substring(0, txtMovMntD.Text.Length -1);

[Jvan]

Text is a property, not a variable. SetLength only works on variables. You can get a valua via the property and set a value to it, so one Alternative could be:

Code: Pascal  [Select][+][-]

1. txtMovMntD.Text := txtMovMntD.Text.Substring(0, txtMovMntD.Text.Length -1);

I have this error message: "Error: Illegal qualifier"

[TRon]

I have this error message: "Error: Illegal qualifier"

In case you have unit sysutils in your uses clause and are using freepascal 3.2.0 or newer then it is because text is of type tcaption(=ttranslationstring), which isn't a string so the helper isn't available I guess.

In that case you could try casting text as a string before the code tries to access the stringhelper.

[jamie]

he wants to simply delete the last character at the end of the string of a TEDIT I would guess..


 For example

 If Not_A_Valid_Number THen
 
      EDIT.TEXT := Copy(EDIT.TEXT, 1, Length(EDIT.TEXT)-1);

[Jvan]

That works. Thanks.