Can we use boolean operator in Delphi XE2 LiveBinding expression?

Question

I am planning to write a Live Binding source expression for TCheckBox:

SourceExpression = '(Checked = False) and (Enabled = True)'

When execute the code, an exception prompted:

Expected EOF - trailing text in expression

Is Delphi XE2 Live Binding support boolean operator?

Just a wild guess - have you tried to use `SourceExpression = '(not Checked) and (Enabled)'` ? And why ? Because it hurts my eyes whenever I see `=` in boolean expression :-) But don't have Delphi XE2 right now... — TLama, Aug 03 '12 at 09:29
Look at this SO question: [How to write live binding expression that control TEdit.PasswordChar based on TCheckBox.Checked?](http://stackoverflow.com/q/11573434/576719). The accepted answer registers a boolean expression evaluator. — LU RD, Aug 03 '12 at 11:17
AFAIK you can't use the logical operators (`and`, `or`, ´not´ , ´xor´, ´shl´, ´shr´) in a LiveBinding expression :(, as workaround you can register a custom method to evaluate the logical operation. — RRUZ, Aug 03 '12 at 18:32
shl and shr are not logical operators. It's impossible to believe that live bindings don't support logical operators. — David Heffernan, Dec 04 '12 at 16:28

score 1 · Answer 1 · edited Jun 10 '16 at 17:59

No, boolean operators are not supported directly.

From the docu:

You can use the following math symbols in your expressions:

Constants: nil True False Pi

Arithmetic operators: + - * /

Logic operators: = <> < <= > >=

Parentheses, (), to change operator precedence.

But you can use the builtin functions IfAll(), IfAny() and IfThen() instead of and, or and not:

SourceExpression := 'IfAll(IfThen(Checked, False, True), Enabled)'

Or you register your own functions.

I tested this 4 XE4, but it should work for XE2 2.

A or B: IfAny(A, B)
A and B: IfAll(A, B)
not A: IfThen(A, False, True)
A xor B: IfAll(IfAny(A, B), IfThen(IfAll(A,B), False, True))

Can we use boolean operator in Delphi XE2 LiveBinding expression?

1 Answers1