[DUG] Enable CheckBox

[John Bird]

A couple of thoughts on this:

1 - If you want to test its empty it may be more general to go

DBCheckBox4.Enabled := not (trim(DBEdit2.Text) = '') ;



I think as it is it should be OK in this case if the underlying data for DBEdit2 is null, but you may want to check that as well, as a null value can stuff up tests like this sometimes.



2 - A non-initialised DBCheckBox4 can behave a little oddly - it may show as looking disabled simply because the value of DBCheckBox4.checked is seen as neither true nor false.  This can happen in D5, not sure about later versions.   You may need to initialise it specifically, and check the AllowGrayed property as well.



John Bird
JBCL
Contact:
johnkbird at paradise.net.nz
jbclnz at xtra.co.nz
027 4844528
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  ----- Original Message ----- 
  From: David O'Brien 
  To: NZ Borland Developers Group - Delphi List 
  Sent: Tuesday, April 27, 2010 10:52 AM
  Subject: Re: [DUG] Enable CheckBox


  Why the four quotes in the false and a space in the true?

   

  I would use something like:

   

  DBCheckBox4.Enabled := not (DBEdit2.Text = '') ;

   

  From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz] On Behalf Of Bob Pawley
  Sent: Tuesday, 27 April 2010 10:39 a.m.
  To: NZ Borland Developers Group - Delphi List
  Subject: [DUG] Enable CheckBox

   

  Hi

   

  I am attempting to enable a checkbox only when a DBEdit has a value. (Disabled when no string in DBEdit.)

   

  Following is my code which disables the CheckBox after a delete from the DBEdit.

   

  But it is not enabled when I add a string to the DBEdit.

  ------

  procedure TForm4.DBEdit2Change(Sender: TObject);
  begin

   

       if
    DBEdit2.Text = ' '

   

    then
    DBCheckBox4.Enabled := True

   

    Else if DBEdit2.Text = ''''

   

    then
     DBCheckBox4.Enabled := False ;

   

  end;

   

  Thanks for any help.

   

  Bob



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