[DUG] Enable CheckBox
Jolyon Smith
jsmith at deltics.co.nz
Tue Apr 27 12:34:00 NZST 2010
Maybe it's just me, but "A doesn't equal B" surely reads more closely to the
real meaning than "not (A does equal B)".
Apart from anything else, the latter requires parentheses to avoid the
compiler getting confused and trying to do : "(Not A) equals (B)". i.e. the
latter syntax is also to the compiler less close to the real meaning (since
it requires disambiguation).
>From a human perspective the scanning is more fluid: A <> B, reads left to
right entirely as intended: "A does not equal B".
NOT (A = B) on the other hand requires me to read it like a syntax tree
parser: "NOT " . (OK, store the fact that I have to logically invert what
follows, keep a mental note of parentheses) . then what follows is "( A is
equal to B )" , right OK, so "A is equal to B inverted", i.e. A does not
equal B.
In other words, exactly what is menat literally and clearly when I write. A
<> B.
But as I say, maybe it's just me.
NOT (I think like a computer).
;)
From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz] On
Behalf Of David O'Brien
Sent: Tuesday, 27 April 2010 11:54 a.m.
To: NZ Borland Developers Group - Delphi List
Subject: Re: [DUG] Enable CheckBox
Mainly because it makes me think about the real meaning when looking at the
code again J.
From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz] On
Behalf Of Colin Johnsun
Sent: Tuesday, 27 April 2010 11:47 a.m.
To: NZ Borland Developers Group - Delphi List
Subject: Re: [DUG] Enable CheckBox
I like David's version but why not get rid of the "not" to:
DBCheckBox4.Enabled := DBEdit2.Text <> '';
Cheers,
On 27 April 2010 09:40, Ian Drower <idrower at gmail.com> wrote:
Hi Bob
I'd use
if DBEdit2.Text <> '' then
DBCheckBox4.Enabled := true
else
DBCheckBox4.Enabled := false
Ian
On 27/04/2010 10:52 a.m., David O'Brien wrote:
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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